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Titanium aluminide components fabricated by wire-laser directed energy deposition (DED-LB/M) with a high deposition rate of ~ 205 cm3 * h-1 are investigated. To minimize oxidation during processing, deposition is conducted under vacuum with argon (Ar) shielding. The effect of substrate preheating on reducing thermal gradients and promoting room-temperature (RT) ductility was explored. Microstructures are characterized using optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and X-ray diffraction (XRD). In the as-deposited condition, the microstructure is heterogeneous, comprising large spheroidal regions of gamma-TiAl alongside smaller equiaxed grains containing an alpha2/gamma lamellar structure. Heat treatment at 1375°C for 2h produces a fully alpha2/gamma lamellar microstructure within very uniform, equiaxed grains (∼0.5–2 mm). The interlamellar spacing is 100–400 nm. In the heat-treated condition, a homogeneous hardness distribution of 300–350 HV1 is obtained across the entire deposited block.
This study investigates the thermal behavior of poly(limonene carbonate) (PLimC), focusing on three main areas: molecular mobility, pyrolysis, and flammability. Considering its molecular structure, a key objective is to compare the properties of PLimC with those of conventional polyolefins (PO) and bisphenol A polycarbonate (PC), while also examining the role of the plasticizer in PLimC and the effect of molecular weight. Molecular mobility was analyzed using broadband dielectric spectroscopy (BDS) and differential scanning calorimetry (DSC); pyrolysis by thermogravimetric analysis (TGA), Fourier-transform infrared (FTIR) spectroscopy, and pyrolysis gas chromatography-mass spectrometry (Py-GC-MS); and flammability by cone calorimeter, bomb calorimeter, UL 94, and limiting oxygen index (LOI). Three relaxation processes were identified by BDS: γ (low temperature), β (intermediate), and α (near glass transition temperature). Higher molecular weight increased the cooperativity of the α relaxation mobility due to chain entanglements. Plasticizers counteract this effect by increasing free volume and reducing intermolecular interactions, leading to less cooperative molecular dynamics and stronger glass-forming behavior. PLimC resembles polyolefins in its lack of char formation and low LOI (17.2 vol.-% O₂), but its decomposition pathway and effective heat of combustion (29.3 MJ kg-1) are similar to those of PC, producing CO₂ and limonene oxide derivatives. Notably, PLimC has a lower decomposition temperature (242–243 °C). These findings provide a foundation for developing effective flame retardant strategies tailored to PLimC’s hybrid thermal behavior, sharing characteristics of both PO and PC.
Hydrogen uptake in complex multicomponent alloys, including high-entropy alloys (HEAs), governs both hydrogen storage capacity and resistance to hydrogen-induced degradation. We combine high-pressure experiments, density-functional theory (DFT), and a GRACE universal interatomic potential to investigate hydrogen absorption in Al0.3CoCrFeNi and Al CoCrFeNi HEAs. In Has a pressure-transmitting medium, the FCC Al0.3CoCrFeNi alloy forms hydrides at ambient temperature above 3 GPa, whereas the Al-rich B2 Al CoCrFeNi alloy shows no evidence of hydride formation even upon heating at pressures up to 50 GPa. Experiments and calculations show that aluminum suppresses hydrogen uptake by increasing solution energies and destabilizing interstitial sites. The universal potential, employed in the calculations and pretrained on large DFT databases, closely reproduces DFT energetics and demonstrates transferability from the dilute limit to the hydride-forming regime. Simulations further disentangle the roles of local ordering, volume changes, composition, and crystal structure. Overall, our results indicate that hydrogen solubility in Al-containing HEAs is governed primarily by composition, with Al-driven B2 ordering as a strong secondary effect.
Although mechanochemical synthesis offers a sustainable way to produce solid forms of pharmaceutical compounds, the molecular-level mechanisms that govern solvent-mediated transformations remain largely unexplored. In this study, we present an in situ solid-state nuclear magnetic resonance (NMR) approach to directly monitor the evolution of liquid-assisted grinding reactions under magic-angle spinning conditions. Using a modified CLASSIC NMR protocol, we tracked the cocrystallization of two model systems, theophylline–benzamide and metronidazole–gallic acid, in the presence of solvents with different levels of polarity. This method allows us to observe both the solid and liquid phases within the reaction environment simultaneously, revealing transient intermediates, hydrate formation, and solvent-dependent polymorphic outcomes. Comparisons with time-resolved in situ X-ray diffraction confirm the complementary nature of NMR in capturing mechanistic details that are otherwise inaccessible to a diffraction-based analysis. This work establishes solid-state NMR as a powerful and accessible in situ tool for investigating the effects of solvents in mechanochemical synthesis, thereby advancing our molecular understanding of polymorphic control and reaction pathways.
A nickel‐based metal–organic framework (Ni‐MOF) with mixed N‐ and O‐donor linkers was synthesized via both mechanochemical and solvothermal routes and evaluated as an electrocatalyst for alcohol oxidation reactions (AORs). Despite having identical crystal and electronic structures, the mechanochemically synthesized Ni‐MOF (termed as MC‐MOF) exhibited markedly superior catalytic activity compared to its solvothermally synthesized analog (ST‐MOF). Structural characterization confirmed that enhanced performance arises from the distinct morphology and higher density of accessible Ni active sites in MC‐MOF. Specifically, the MC‐MOF exhibited a roughly 4.4‐fold higher electrochemically active surface area, enabling the highly stable, selective oxidation of various alcohols to valuable products over 24 h of continuous operation. Operando quick X‐ray absorption spectroscopy revealed that under alkaline conditions, MC‐MOF undergoes potential‐dependent structural evolution, displaying distinct catalytic pathways for oxygen evolution and AORs. While Ni centers oxidize to higher valence states during the oxygen evolution reaction, they remain largely in the Ni
2+ state during AORs, indicating selective suppression of high‐valent Ni‐oxygenated species in the presence of alcohol molecules in the electrolyte medium. This study demonstrates that mechanochemical synthesis can effectively tailor the morphology and catalytic behavior of MOF‐based electrocatalysts, offering an environmentally benign and scalable route for developing advanced materials for sustainable energy conversion.
Infrared thermography enables non-destructive defect detection by analyzing transient temperature distributions caused by heat flow interacting with internal structures or inhomogeneities. An equivalent way of describing this interacting heat flow is the propagation of thermal waves inside a sample. However, a key limitation is the diffuse nature of thermal waves, which are measured only at the surface and lose spatial resolution with increasing depth - unlike propagating ultrasound waves. This restricts thermography’s effectiveness in identifying small or deep defects. A promising solution aiming to enhance spatial resolution, detection sensitivity, and reconstruction quality involves shaping thermal wave fields using laser thermography. We present the latest results of this technology by employing high-power laser systems and modern numerical methods.
Representing experimental procedures in an unambiguous way that can be understood and reproduced by other scientists is at the heart of scientific progress. For centuries, these descriptions were made by humans and for humans, often assuming implicit or tacit knowledge. However, when Materials Acceleration Platforms (MAPs) and Self-Driving Labs (SDLs) are used for the autonomous discovery and optimization of materials, sharing knowledge, and workflows that were designed and executed by machines becomes increasingly important. These machines require an explicit, precise and accurate description and modeling of all process parameters and steps that need to be executed. To address these needs, especially in the domain of materials science and nano and advanced materials synthesis, we developed the Wet Chemical Synthesis Ontology (WCSO), which is based on the Platform MaterialDigital core ontology (PMDco) and the Basic Formal Ontology (BFO). The ontology contains recurring concepts from millions of wet chemical synthesis procedures in the scientific literature. We discuss the design considerations, concepts, and architecture of our ontology in detail, and demonstrate how it can be applied to the construction and querying of semantically annotated knowledge graphs from wet chemical nano- and advanced materials synthesis workflows that were previously designed for and then executed on an SDL. Using such formal representations and semantic annotations for describing synthesis procedures and workflows facilitates the reproducibility, sharing, and execution of synthesis procedures across different labs around the world that use different orchestrators for their robotic hardware.
Oligo(butylene terephthalate)s with degrees of polymerization (DP) ranging from 15 to 20 were synthesized via Ti(OEt)4-catalyzed transesterification in bulk, using either an excess of 1,4-butanediol or dimethyl terephthalate. The PBTs were annealed at 190 °C and 210 °C, either in the absence or presence of catalysts, such as tin(II) 2-ethyl hexanoate, Bu2SnO, and Zr(acac)4. The solid-state reactions were monitored by matrix-assisted laser desorption/ionization time-of-flight (MALDI TOF) mass spectrometry, which allowed differentiation between different end-group combinations. Furthermore, the reaction products were characterized using gel permeation chromatography (GPC) and differential scanning calorimetry (DSC) measurements. Solid-state polycondensation (SSP) primarily proceeded by the reaction of chains with CH2OH end groups due to the formation of loops on the crystallite surface. In contrast, a predominance of methyl ester end groups proved unfavorable for the progress of the SSP. Under optimized conditions, SSP increased the molecular weight by a factor of eight and involved formation of cycles with a strong tendency toward formation of monodisperse extended-ring crystallites.
Additive Manufacturing (AM) process has been widely adopted to create more efficient items through a better design. The consideration comes not only from the material selection but also the structural perspective that caters to specific applications. Triply Periodic Minimal Surfaces (TPMS) is a design that allows any shapes to have more contact surface area and simultaneously improving the load-bearing capacity of a structure. Having a better understanding on how such structures deteriorate is essential for predicting their strength and their potential lifetime. The in-situ XCT experiment was carried out using the DEBEN 20kN rig to investigate the damage mechanisms. An open-source Digital Volume Correlation (DVC) module named SPAM is used to compute these CT images taken at different loading points. This result could then be correlated with the morphological description to find the weak spots inside the structures.
In our study, we investigated the mechanochemical cocrystallization of pimelic acid (PA) with pyrazinamide (PZA) and nicotinamide (NIC) using in situ PXRD. Cocrystallization kinetics were affected by milling temperature and pre-milling of PA, due to PA polymorphism. Our results highlight the value of synchrotron radiation in situ PXRD for understanding mechanochemical reaction mechanisms.