MRS Communications最新文献

Abstract

In this paper, we investigate the morphology of ionic poly(dimethylsiloxane) silica nanocomposites of randomly grafted or chain-end-functionalized ionic PDMS melts using atomistic MD simulations. The localization of the charge alters the structure and dynamics of ionic PDMS chains near the nanosilica surface. The chain-end ionic PDMS obtains the largest dimensions, whereas the charge fraction of 10% of the random ionic copolymers leads to a contraction of PDMS chains. The charge fraction dramatically alters the dynamics of the ionic PDMS chains, although they reach the diffusive regime. An anisotropy of PDMS chain dynamics perpendicular and parallel to the nanosilica and an heterogeneity of PDMS dynamics from the nanosilica surface are observed for the longer randomly grafted and chain-end ionic PDMS chains. The longer randomly grafted ionic PDMS chains are strongly adsorbed in the vicinity of the nanosilica surface.

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Porous materials are pivotal in emerging fields like tissue engineering, scaffold, and drug delivery due to their distinctive porosity-driven functional properties. This paper describes how to achieve multiscale porosity in food-based composites through a thermally activated gelatinization process of amylopectin molecules coupled with 3D printing. By controlling printing paths, macropores are engineered, while degree of gelatinization governs micro- and nanopores formation. Process-microstructure relationship reveals that longer preheating treatments at higher gelatinization temperatures significantly reduce micro-pore area by over twofold and nanopore surface area by over threefold. These results provide a promising route to fabricate food-based composite with tailorable microstructures.

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Scaffold-guided bone regeneration (SGBR) is a rapidly developing field that aims to address the clinical challenges in reconstructive surgery. Combining ceramics with biodegradable polymers offers a wide range of physico-chemical properties, but their mechanical properties are far from the expectations. Nature offers examples of mineralized materials with excellent mechanical properties. This can be attributed to their unique architecture featuring soft polymeric interfaces that deflect propagating cracks. The present article depicts the role of soft interfaces on bone toughness, the governing equations of cracks propagating at interfaces, and provide guidelines for the design of medical grade composites for SGBR.

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Ni, Pt, and NiPt catalysts supported on SBA-15 were synthesized, characterized, and tested in anisole hydrodeoxygenation to determine the effect of the metal’s nature on the catalytic activity in the hydrogenation of the aromatic ring of anisole and hydrogenolysis of the C–O bond in the cyclohexyl methyl ether intermediate. Metal loadings in the catalysts were 5 wt% of Ni and 1 wt% of Pt. The bimetallic NiPt/SBA-15 catalyst showed the highest catalytic activity in both hydrogenation and hydrogenolysis, attributed to the promotional effect of Pt on NiO reduction and the formation of a Ni–Pt alloy with better dispersion of metal nanoparticles.

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Abstract

The transition from heterogeneous nucleation of nanoscale hardening S-phase precipitates on dislocation lines in cold-rolled aluminium alloy 2024 (Al–Cu–Mg) to a spatially homogeneous distribution during artificial ageing is studied by means of in situ and ex situ transmission electron microscopy (TEM). Three stages of precipitate evolution following nucleation on dislocation lines are established: (i) Growth and coalescence on dislocation lines, (ii) Ostwald ripening controlled by pipe diffusion, and (iii) Ostwald ripening controlled by volume diffusion. Whilst Ostwald ripening controlled by pipe diffusion is active (stage (ii) and transition from stage (ii) to stage (iii)) dislocation annihilation and/or re-arrangement can occur.

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The functionalization of polymeric matrices through graft polymerization offers various advantages by providing new properties, allowing for additional chemical reactions that the matrix alone could not undergo or that would require drastic chemical conditions to occur. In this work, epoxy groups were incorporated through a graft polymer of poly(glycidyl methacrylate), using a prefunctionalization with peroxide groups in the polytetrafluoroethylene matrix through gamma radiation. These peroxide groups were subsequently used as radical chemical initiators in the graft polymerization reaction of glycidyl methacrylate. The graft polymerization reaction was studied based on the absorbed dose, monomer concentration, reaction time, and temperature.

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Detecting and analyzing various defect types in semiconductor materials is an important prerequisite for understanding the underlying mechanisms and tailoring the production processes. Analysis of microscopy images that reveal defects typically requires image analysis tasks such as segmentation and object detection. With the permanently increasing amount of data from experiments, handling these tasks manually becomes more and more impossible. In this work, we combine various image analysis and data mining techniques to create a robust and accurate, automated image analysis pipeline for extracting the type and position of all defects in a microscopy image of a KOH-etched 4H-SiC wafer.

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Photoluminescence (PL) mapping was utilized to investigate damage in β-Ga₂O₃ epilayers induced by 1064 nm laser pulses. The intensity and position of the intrinsic UV band were determined and plotted as a false-color image. Two types of damage were identified: circular damage and damage cracks. Circular damage shows lower UV PL intensity than the surrounding material with color centers in a “halo” around the damaged region. Damage cracks are aligned with the a and c axes and show higher PL intensity than undamaged material. Defects in the as-grown material were revealed by shifts in the UV band energy.

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During coal storage and transportation, spontaneous combustion occurs occasionally. Heat pipes, as new fire prevention technology, have been applied and explored in the prevention and control of spontaneous combustion in coal yards. This paper combines the mechanism of spontaneous combustion in coal yards and the advantages and disadvantages of traditional prevention methods to explain the advantages of heat pipe technology, summarizes and analyzes factors affecting the heat transfer efficiency of gravity heat pipes, such as working medium, arrangement, heat pipe structure, and external environment, and looks forward to the development trend of gravity heat pipes in coal yards.

Graphical Abstract