Material Characterization Techniques Research Articles

New Directions for Thermoelectrics: A Roadmap from High‐Throughput Materials Discovery to Advanced Device Manufacturing

Thermoelectric materials, which can convert waste heat into electricity or act as solid‐state Peltier coolers, are emerging as key technologies to address global energy shortages and environmental sustainability. However, discovering materials with high thermoelectric conversion efficiency is a complex and slow process. The emerging field of high‐throughput material discovery demonstrates its potential to accelerate the development of new thermoelectric materials combining high efficiency and low cost. The synergistic integration of high‐throughput material processing and characterization techniques with machine learning algorithms can form an efficient closed‐loop process to generate and analyze broad datasets to discover new thermoelectric materials with unprecedented performances. Meanwhile, the recent development of advanced manufacturing methods provides exciting opportunities to realize scalable, low‐cost, and energy‐efficient fabrication of thermoelectric devices. This review provides an overview of recent advances in discovering thermoelectric materials using high‐throughput methods, including processing, characterization, and screening. Advanced manufacturing methods of thermoelectric devices are also introduced to realize the broad impacts of thermoelectric materials in power generation and solid‐state cooling. In the end, this article also discusses the future research prospects and directions.

Low‐Carbon‐Footprint Plasma‐Functionalized Coconut‐Coir‐Based Porous Carbon as an Efficient and Sustainable Adsorbent

AbstractHerein, the surface of pyrolyzed coconut coir (PCC) dust has been functionalized using atmospheric plasma under non‐equilibrium conditions without utilizing vacuum chambers. The reactive species present in the plasma such as, molecular ions, electrons, and radicals interact with PCC's surface, leading to the introduction of epoxy, carbonyl and amino functional groups on carbon surface. The resulting plasma functionalized carbon (PFC) material was characterized using several advanced material characterization techniques, including PXRD, FTIR, XPS, N2 BET specific surface area, SEM and TEM imaging techniques, etc. Moreover, it has been used in diverse applications in toxic gas removal (CO2, CO, NOx), fluoride (F−) removal from drinking water and cationic organic dye (methylene blue–MB) removal. The reported method for synthesis of functional carbon introduces a platform technology for low carbon footprint, green synthesis of advanced functional materials.

Shear strength recovery of sand with self-healing polymeric capsules

Self-healing approaches are increasingly being explored in various fields as a potential method to recover damaged material properties. By self-recovering without external intervention, self-healing techniques emerge as a potential solution to arrest or prevent the development of large strains problems in soils (e.g., landslides) and other ground effects that influence the serviceability of structures (e.g., differential settlement). In this study, a microcapsule-based self-healing sand was developed, and its performance during mixing and compaction, shearing, and recovery of shear strength was demonstrated. The cargo used for sand improvement, a hardening oil, tung oil, was encapsulated in calcium alginate capsules by the ionic gelation method. The surface properties, internal structure, thermal stability and molecular structure of the capsules were evaluated by advanced material characterization techniques. The survivability of capsules during mixing and compaction was assessed by measuring the content of tung oil released into the sand, while their influence on sand shear strength and its recovery was assessed with shear box tests. The results showed that the capsules could rupture due to movement of the sand particles, releasing the tung oil cargo, leading to its hardening and minimizing its strain-softening response and enhancing up to 76% of the sand shear strength (at a normal stress of 10 kPa and capsules content of 4%). This study demonstrates the potential of a capsules-based self-healing system to provide ‘smart’ autonomous soil strength recovery and thus with potential to actively control the large strain behavior of soils.

Enhanced solar Photocatalysis: Zinc oxide modified Yb2Zn-TiO6 doped g-C3N4 heterostructures for bromothymol blue mineralization and bacterial inhibition

A new composite material, ZnO/Yb2Zn-TiO6@g-C3N4 has been synthesized by simple hydrothermal process. This composite has been characterized using various material characterization techniques and was found to have a heterojunction amongst Yb2Zn-TiO6 and g-C3N4, leading to higher light absorption and poorer charge carrier recombination rates. Furthermore, the evaluation of the charge carrier density revealed that the incorporation of small sized ZnO (40 nm) into Yb2Zn-TiO6@g-C3N4 led to heightened disintegration of the photoinduced charge carriers. This observation implies that the presence of said metal oxide enhances the photocatalytic performance by greatly promoting the effective separation of charge carriers for various applications. When tested with bromothymol blue, the 20 wt% ZnO/Yb2Zn-TiO6@g-C3N4 composite showed a photodegradation rate several times greater (98 %) than individual ZnO, C3N4 and Yb2Zn-TiO6, respectively. The degradation efficiency of the ZnO/Yb2Zn-TiO6@g-C3N4 nanostructure in the absence of light was 24 %. The increased photoactivity of the composite material is due to the efficient separation of charge carriers and also due to the high redox capabilities resulting from the heterojunction. The composite also demonstrated stable photocatalytic performance over five cyclic runs and was effective in treating real printed ink wastewater. Furthermore, ZnO/Yb2Zn-TiO6@g-C3N4 was found to have excellent antibacterial properties in opposition to Escherichia coli, (Inhibition = 16(±0.2) mm) as well as Bacillus subtilis (Inhibition = 22(±0.3) mm). The MIC of the said nanomaterials against Escherichia coli as well as Bacillus subtilis were 50 µg/mL and 30 µg/mL respectively. The detailed explanation of the photodegradation mechanism was also provided. The use of this composite material can help to reduce the harmful effects of contaminants and microbes in aquatic environments and promote environmental sustainability.

Characterization of Microstructural and Mechanical Properties of 17-4 PH Stainless Steel by Cold Rolled and Machining vs. DMLS Additive Manufacturing

The 17-4 PH stainless steel is widely used in the aerospace, petrochemical, chemical, food, and general metallurgical industries. The present study was conducted to analyze the mechanical properties of two types of 17-4 PH stainless steel—commercial cold-rolled and direct metal laser sintering (DMLS) manufactured. This study employed linear and nonlinear tensile FEM simulations, combined with various materials characterization techniques such as tensile testing and nanoindentation. Moreover, microstructural analysis was performed using metallographic techniques, optical microscopy, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The results on the microstructure for 17-4 PH DMLS stainless steel reveal the layers of melting due to the laser process characterized by complex directional columnar structures parallel to the DMLS build direction. The mechanical properties obtained from the simple tension test decreased by 17% for the elastic modulus, 7.8% for the yield strength, and 7% for the ultimate strength for 17-4 PH DMLS compared with rolled 17-4 PH stainless steel. The FEM simulation using the experimental tension test data revealed that the 17-4 PH DMLS stainless steel experienced a decrease in the yield strength of ~8% and in the ultimate strength of ~11%. A reduction of the yield strength of the material was obtained as the grain size increased.

Resonant ultrasound spectroscopy experimental design and optimization

Resonant Ultrasound Spectroscopy (RUS) is a nondestructive material characterization technique that utilizes solid body resonances to estimate elastic moduli. This method is advantageous over traditional mechanical testing due to the significantly lower number of required samples to estimate the same number of moduli. The goal of this project is to develop a high-throughput RUS system capable of measuring experimental resonances and mode shapes in a fraction of the time of traditional RUS measurements. A new system was designed which leverages data/image analysis algorithms to aid in sample alignment and data collection. A standardized sample geometry was also analyzed by performing a geometric sensitivity study and optimizing the aspect ratio of lengths of a parallelepiped. The results show that the optimized sample geometry is consistent between materials with varying elastic properties. In order to validate the design of the new RUS system a comparative study to an existing system was conducted. The results show that the newly designed system produces comparable resonant frequency and mode shape measurements.

Microstructure Study on Very High Cycle Fatigue of an Additively Manufactured Aluminium Alloy via Advanced Characterization Methods

The engineering application of additively manufactured (AM) metallic materials is quite limited by their fatigue behaviors, which are very inconsistent with that of conventionally wrought or cast ones. Here, based on advanced material characterization techniques, such as focused ion beam (FIB), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), the microstructures underneath fracture surfaces were thoroughly investigated in an AM aluminum (AlSi10Mg) alloy with horizontal and vertical building orientation enduring very high cycle fatigue (VHCF) loading under the stress ratios R = −1, 0, and 0.5. Two VHCF failure specimens A and B were representatively selected to further examine SEM and TEM sample preparation via FIB milling. Specimen A was horizontally printed and failed at R = −1; specimen B was vertically printed and failed at R = 0. TEM samples A1 and B1 were lifted from locations near the crack initiation sites on the fracture surfaces of specimens A and B; The locations of TEM samples A2 and B2 kept away from the crack origin sites but still within the “fish-eye” region of crack steady growth. TEM observations show that there was no characteristic microstructure induced by VHCF in different oriented specimens and under various R values.

A Methodology for the Rapid Qualification of Additively Manufactured Materials Based on Pore Defect Structures

Additive manufacturing (AM) can create net or near-net-shaped components while simultaneously building the material microstructure, therefore closely coupling forming the material and shaping the part in contrast to traditional manufacturing with distinction between the two processes. While there are well-heralded benefits to AM, the widespread adoption of AM in fatigue-limited applications is hindered by defects such as porosity resulting from off-nominal process conditions. The vast number of AM process parameters and conditions make it challenging to capture variability in porosity that drives fatigue design allowables during qualification. Furthermore, geometric features such as overhangs and thin walls influence local heat conductivity and thereby impact local defects and microstructure. Consequently, qualifying AM material within parts in terms of material properties is not always a straightforward task. This article presents an approach for rapid qualification of AM fatigue-limited parts and includes three main aspects: (1) seeding pore defects of specific size, distribution, and morphology into AM specimens, (2) combining non-destructive and destructive techniques for material characterization and mechanical fatigue testing, and (3) conducting microstructure-based simulations of fatigue behavior resulting from specific pore defect and microstructure combinations. The proposed approach enables simulated data to be generated to validate and/or augment experimental fatigue data sets with the intent to reduce the number of tests needed and promote a more rapid route to AM material qualification. Additionally, this work suggests a closer coupling between material qualification and part certification for determining material properties at distinct regions within an AM part.

Electrochemical deposition of hydrothermally pretreated TiO2 on aluminium substrate through the formation of peroxotitanium complex and their application towards visible light assisted photocurrent generation

Herein, we report a novel method for the electrochemical deposition of TiO2 on Al substrate through the formation of peroxotitanium complex without any post heat treatment process. The alkaline treated titanium precursors were used as an electrolyte and TiO2 was deposited onto aluminium substrate by both cathodic reduction and electrophoretic deposition through the formation of peroxotitanium complex. The electrodeposition process was optimized by varying the pH, concentration of the electrolyte, deposition voltage, time and area of the electrode respectively. The optimized condition to obtain a maximum yield is as follows: voltage (4.5 V), time (2.5 h), pH (5) and area of the electrode 3 × 3 cm2. The deposits were then characterized using various material characterization techniques such as high-resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and Raman spectroscopy respectively. The morphological analysis showed the deposition of nanocrystalline TiO2 with irregular morphology on Al substrate. The AFM revealed a non-uniform deposition of TiO2 with high surface roughness (average roughness: 44.60 nm). The XRD pattern and Raman spectrum confirmed the presence of anatase phase of TiO2. The obtained TiO2 were then subjected to photoelectrochemical studies by coating over an ITO electrode. The nanocrystalline TiO2 showed excellent photocurrent response which could be due to the short hole retrieval and fast electron transport across the electrode-electrolyte interface. The proposed method can be promising towards the industrial application for the extraction and recovery of TiO2 from the mineral ore residues and spent mining waste.

Effects of laser welding on the martensitic transformation of a shape-memory Ti-Ni alloy

The objective of this study is to investigate the martensitic transformation behavior of a Ti-Ni alloy subjected to a laser welding process. Materials characterization techniques were used to analyze the influences of this welding procedure on the phase transformation behavior. This study can provide valuable insights for the improvement of Ti-Ni alloy welding processes used for technological applications, such as in the aerospace industry. In this study, samples were prepared under three conditions: thermal treatment at 400°C, thermal treatment at 500°C, and as-received. The characterization techniques used were: Optical Microscopy (OM), Differential Scanning Calorimetry (DSC), Electron Dispersion Spectroscopy (EDS), X-Ray Diffraction (XRD), and Vickers Microhardness (HV). The results allow for analysis of thermoelastic martensitic transformation and variations in the compositions of the alloy elements. The research, in general, aims to repurpose welding waste in Ti-Ni alloys for the production of mini sensors. The enthalpy was higher for the alloy treated at 500°C and welded. The research findings led to the observation of martensitic phase transformation in the laser-welded Ti-Ni alloy, which suggests that it can be used as a sensor/actuator.

Water-Resistance-Based S-Scheme Heterojunction for Deep Mineralization of Toluene.

Deep mineralization of low concentration toluene (C7 H8 ) is one of the most significant but challenging reactions in photocatalysis. It is generally assumed that hydroxyl radicals (⋅OH) as the main reactive species contribute to the enhanced photoactivity, however, it remains ambiguous at this stage. Herein, a S-scheme ZnSn(OH)6 -based heterojunction with AlOOH as water resistant surface layer is in situ designed for tuning the free radical species and achieving deep mineralization of C7 H8 . By employing a combination of in situ DRIFTS and materials characterization techniques, we discover thatthe dominant intermediates such as benzaldehyde and benzoic acid instead of toxic phenols are formed under the action of holes (h+ ) and superoxide radicals (⋅O2 - ). These dominant intermediates turn out to greatly decrease the ring-opening reaction barrier. This study offers new possibilities for rationally tailoring the active species and thus directionally producing dominant intermediates via designing water resistant surface layer.

Water‐Resistance‐Based S‐Scheme Heterojunction for Deep Mineralization of Toluene

AbstractDeep mineralization of low concentration toluene (C7H8) is one of the most significant but challenging reactions in photocatalysis. It is generally assumed that hydroxyl radicals (⋅OH) as the main reactive species contribute to the enhanced photoactivity, however, it remains ambiguous at this stage. Herein, a S‐scheme ZnSn(OH)6‐based heterojunction with AlOOH as water resistant surface layer is in situ designed for tuning the free radical species and achieving deep mineralization of C7H8. By employing a combination of in situ DRIFTS and materials characterization techniques, we discover that the dominant intermediates such as benzaldehyde and benzoic acid instead of toxic phenols are formed under the action of holes (h+) and superoxide radicals (⋅O2−). These dominant intermediates turn out to greatly decrease the ring‐opening reaction barrier. This study offers new possibilities for rationally tailoring the active species and thus directionally producing dominant intermediates via designing water resistant surface layer.

Defect engineering of carbon-based electrocatalysts for the CO2 reduction reaction: A review

Electrocatalytic carbon dioxide (CO2) reduction is an important way to achieve carbon neutrality by converting CO2 into high-value-added chemicals using electric energy. Carbon-based materials are widely used in various electrochemical reactions, including electrocatalytic CO2 reduction, due to their low cost and high activity. In recent years, defect engineering has attracted wide attention by constructing asymmetric defect centers in the materials, which can optimize the physicochemical properties of the material and improve its electrocatalytic activity. This review summarizes the types, methods of formation and defect characterization techniques of defective carbon-based materials. The advantages of defect engineering and the advantages and disadvantages of various defect formation methods and characterization techniques are also evaluated. Finally, the challenges of using defective carbon-based materials in electrocatalytic CO2 reduction are investigated and opportunities for their use are discussed. It is believed that this review will provide suggestions and guidance for developing defective carbon-based materials for CO2 reduction.

Gamma-ray Spectroscopy in Low-Power Nuclear Research Reactors

Gamma-ray spectroscopy is an effective technique for radioactive material characterization, routine inventory verification, nuclear safeguards, health physics, and source search scenarios. Gamma-ray spectrometers typically cannot be operated in the immediate vicinity of nuclear reactors due to their high flux fields and their resulting inability to resolve individual pulses. Low-power reactor facilities offer the possibility to study reactor gamma-ray fields, a domain of experiments hitherto poorly explored. In this work, we present gamma-ray spectroscopy experiments performed with various detectors in two reactors: The EPFL zero-power research reactor CROCUS, and the neutron beam facility at the Ohio State University Research Reactor (OSURR). We employed inorganic scintillators (CeBr3), organic scintillators (trans-stilbene and organic glass), and high-purity germanium semiconductors (HPGe) to cover a range of typical—and new—instruments used in gamma-ray spectroscopy. The aim of this study is to provide a guideline for reactor users regarding detector performance, observed responses, and therefore available information in the reactor photon fields up to 2 MeV. The results indicate several future prospects, such as the online (at criticality) monitoring of fission products (like Xe, I, and La), dual-particle sensitive experiments, and code validation opportunities.

Mechanochemical enhancement in electrode materials via silver-embedded reduced graphene oxide and cobalt oxide nanostructure for supercapacitor applications

This study delves into the intricate domain of mechanochemical synthesis, employing a developed approach for the fabrication of electrode materials. The method involves the incorporation of silver nanoparticles into a two-dimensional matrix of reduced graphene oxide (RGO) combined with cobalt oxide nanostructures, yielding a zero-dimensional cobalt oxide@RGO.Ag nanocomposite. A comprehensive suite of material characterization techniques, including XRD, SEM, EDX, TEM, XPS, and BET, was used to investigate the synthesized materials. Concurrently, extensive electrochemical investigations, incorporating cyclic voltammetry (CV), galvanic charge–discharge (GCD), electrochemical impedance spectroscopy (EIS), and retention analyses, are applied to the constructed electrochemical cell. The resulting RGO.Ag@Co3O4 nanocomposite exhibits a remarkable specific capacitance of 371.2 F g−1 at a scan rate of 5 mV s−1. In addition, energy density (Ed) and power density (Pd) values of 21.6 Wh/kg and 997 W/kg, respectively, are achieved at a current density (Cd) of 0.5 A g−1.

Hole formation mechanisms in double-sided laser drilling of Ti6Al4V-C/SiC stacked materials

This is the first investigation on the potential of doubled-sided laser drilling for hole making in Ti6Al4V-C/SiC, a hard-to-machine stacked structure that holds critical significance in high-temperature structural applications. While previous literature reported laser drilling-induced microstructural change in Ti6Al4V and C/SiC single sheets respectively, a comprehensive understanding of the melt pool formation process and its influence on hole morphology/quality is still lacking. The complexity increases when Ti6Al4V is coupled with C/SiC in a stacked structure, highlighting a significant yet understudied knowledge gap in understanding the intricate material interactions at the interface. Here we present a multifaceted study combining novel computational fluid dynamics (CFD) modeling approach with ablation mechanism investigation through advanced microstructure analysis. A hybrid CFD modeling strategy integrating volume of fluid method and level set method has been developed to successfully simulate the evolution of hole shape, recast layer formation, and melt pool flow behaviour in Ti6Al4V-C/SiC. This model provides comprehensive insights into molten pool dynamics under various laser drilling conditions, fostering a fundamental understanding of the mechanism that drives recast layer formation and influencing surface quality. To validate our modeling outcomes, extensive experimental investigations were undertaken across a range of laser drilling conditions. Whenever possible, samples were analysed using advanced materials characterization techniques, including scanning electron microscopy, energy dispersive spectroscopy, and electron backscatter diffraction, to elucidate the microstructural evolution within the recast layer and the formation of the heat-affected zone. Whenever possible, the results were also compared with single side drilled Ti6Al4V-C/SiC stacks, Ti6Al4V or C/SiC single sheets (i.e., the benchmark references). Our experimental findings align well with the modeling results, systematically illustrating that doubled-sided laser drilling of the stacked structure outperforms the conventional single-sided laser drilling in terms of hole morphology, surface roughness, and reduced recast layer formation. Despite these promising results, the proposed technology is currently limited to laboratory scales and lacks capacity in manufacturing certain parts with complex geometry. Future outlook has therefore been proposed with potential solution to address these challenges and enable real world applications in future.

Short-Time Magnetron Sputtering for the Development of Carbon-Palladium Nanocomposites.

In recent nanomaterials research, combining nanoporous carbons with metallic nanoparticles, like palladium (Pd), has emerged as a focus due to their potential in energy, environmental and biomedical fields. This study presents a novel approach for synthesizing Pd-decorated carbons using magnetron sputter deposition. This method allows for the functionalization of nanoporous carbon surfaces with Pd nano-sized islands, creating metal-carbon nanocomposites through brief deposition times of up to 15 s. The present research utilized direct current magnetron sputtering to deposit Pd islands on a flexible activated carbon cloth substrate. The surface chemistry, microstructure, morphology and pore structure were analyzed using a variety of material characterization techniques, including X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectroscopy, gas sorption analysis and scanning electron microscopy. The results showed Pd islands of varying sizes distributed across the cloth's carbon fibers, achieving high-purity surface modifications without the use of chemicals. The synthesis method preserves the nanoporous structure of the carbon cloth substrate while adding functional Pd islands, which could be potentially useful in emerging fields like hydrogen storage, fuel cells and biosensors. This approach demonstrates the possibility of creating high-quality metal-carbon composites using a simple, clean and economical method, expanding the possibilities for future nanomaterial-based applications.

Revealing stress-induced changes equivalence between polarization-sensitive optical coherence tomography and polarimetric camera measurements

Polarization-Sensitive Optical Coherence Tomography (PS-OCT) is a widely-used technique for high-resolution material characterization since it allows for real-time structural analysis and imperfections identification. Nevertheless, when the sample is too big or imperfections are not on the micrometric scale, PS-OCT imaging can become too complex to be performed on a regular basis. Alternatively, polarimetric camera (PCam) imaging can obtain polarization measurements of a sample at a macroscopic scale, allowing for a faster and cheaper inspection of the sample. In doing so, the depth-profiling capabilities of PS-OCT would be forfeited, as well as the ability to measure other than the linear polarization qualities of the light beam. This paper compares the data that can be easily extracted from a PCam, with the complete and more complex characterization of the polarization of light that can be obtained with a PS-OCT device. The comparison of both systems is assessed through the evaluation of their performance when measuring different stress states of a sample.

Metal-organic frameworks (MOFs) for photoelectrocatalytic (PEC) reducing carbon dioxide (CO2) to hydrocarbon fuels.

MOF-based photoelectrocatalysis (PEC) using CO2 as an electron donor offers a green, clean, and extensible way to make hydrocarbon fuels under more tolerant conditions. Herein, basic principles of PEC reduction of CO2 and the preparation methods and characterization techniques of MOF-based materials are summarized. Furthermore, three applications of MOFs for improving the photoelectrocatalytic performance of CO2 reduction are described: (i) as photoelectrode alone; (ii) as a co-catalyst of semiconductor photoelectrode or as a substrate for loading dyes, quantum dots, and other co-catalysts; (iii) as one of the components of heterojunction structure. Challenges and future wave surrounding the development of robust PEC CO2 systems based on MOF materials are also discussed briefly.

Backscattering silicon spectrometer (BASIS): sixteen years in advanced materials characterization.

Quasielastic neutron scattering (QENS) is an experimental technique that can measure parameters of mobility, such as diffusion jump rate and jump length, as well as localized relaxations of chemical species (molecules, ions, and segments) at atomic and nanometer length scales. Due to the high penetrative power of neutrons and their sensitivity to neutron scattering cross-section of chemical species, QENS can effectively probe mobility inside most bulk materials. This review focuses on QENS experiments performed using a neutron backscattering silicon spectrometer (BASIS) to explore the dynamics in various materials and understand their structure-property relationship. BASIS is a time-of-flight near-backscattering inverted geometry spectrometer with very high energy resolution (approximately 0.0035 meV of full width at half maximum), allowing measurements of dynamics on nano to picosecond timescales. The science areas studied with BASIS are diverse, with a focus on soft matter topics, including traditional biological and polymer science experiments, as well as measurements of fluids ranging from simple hydrocarbons and aqueous solutions to relatively complex room-temperature ionic liquids and deep-eutectic solvents, either in the bulk state or confined. Additionally, hydrogen confined in various materials is routinely measured on BASIS. Other topics successfully investigated at BASIS include quantum fluids, spin glasses, and magnetism. BASIS has been in the user program since 2007 at the Spallation Neutron Source of the Oak Ridge National Laboratory, an Office of Science User Facility supported by the U.S. Department of Energy. Over the past sixteen years, BASIS has contributed to various scientific disciplines, exploring the structure and dynamics of many chemical species and their fabrication for practical applications. A comprehensive review of BASIS contributions and capabilities would be an asset to the materials science community, providing insights into employing the neutron backscattering technique for advanced materials characterization.