Electric Field‐Induced Oxidation of Ferromagnetic/Ferroelectric Interfaces

Composite multiferroics are a new class of material where magneto‐electric coupling is achieved by creating an interface between a ferromagnetic and a ferroelectric compound. The challenge of understanding the chemical and magnetic properties of such interface is a key to achieve good magneto‐electric coupling. The unique possibilities offered by isotope sensitive techniques are used to selectively investigate the interface's chemistry and magnetism in Fe/BaTiO₃ and Fe/LiNbO₃ systems during the application of an electric field. With a large enough electric field, a strong oxidation of Fe is triggered, which creates a magnetically dead interface. This leads to an irreversible decrease of the magneto‐electric coupling properties. Material parameters are identified that determine under which electric field the interface may be modified. The results are confirmed on the two systems and are expected to be widespread in this new class of hybrid material.     

From flat sheets to curved geometries: Origami and kirigami approaches

Transforming flat sheets into three-dimensional structures has emerged as an exciting manufacturing paradigm on a broad range of length scales. Among other advantages, this technique permits the use of functionality-inducing planar processes on flat starting materials, which after shape-shifting, result in a unique combination of macro-scale geometry and surface topography. Fabricating arbitrarily complex three-dimensional geometries requires the ability to change the intrinsic curvature of initially flat structures, while simultaneously limiting material distortion to not disturb the surface features. The centuries-old art forms of origami and kirigami could offer elegant solutions, involving only folding and cutting to transform flat papers into complex geometries. Although such techniques are limited by an inherent developability constraint, the rational design of the crease and cut patterns enables the shape-shifting of (nearly) inextensible sheets into geometries with apparent intrinsic curvature. Here, we review recent origami and kirigami techniques that can be used for this purpose, discuss their underlying mechanisms, and create physical models to demonstrate and compare their feasibility. Moreover, we highlight practical aspects that are relevant in the development of advanced materials with these techniques. Finally, we provide an outlook on future applications that could benefit from origami and kirigami to create intrinsically curved surfaces.     

Time–Temperature Management Along the Food Cold Chain: A Review of Recent Developments

The cold chain is responsible for the preservation and transportation of perishable foods in the proper temperature range to slow biological decay processes and deliver safe and high‐quality foods to consumers. Studies show that the efficiency of the cold chain is often less than ideal, as temperature abuses above or below the optimal product‐specific temperature range occur frequently, a situation that significantly increases food waste and endangers food safety. In this work, field studies on time–temperature conditions at each critical stage of the cold chain are reviewed to assess the current state of commercial cold chains. Precooling, ground operations during transportation, storage during display at retail and in domestic refrigerators, and commercial handling practices are identified and discussed as the major weaknesses in the modern cold chain. The improvement in efficiency achieved through the measurement, analysis, and management of time–temperature conditions is reviewed, along with the accompanying technical and practical challenges delaying the implementation of such methods. A combination of prospective experimental and modeling research on precooling uniformity, responsive food inventory management systems, and cold chains in developing countries is proposed for the improvement of the cold chain at the global scale.     

Platinum group element concentrations and osmium isotopic composition in urban airborne particles from Boston, Massachusetts

Platinum, Pd, Rh, and Os were found to occur at elevated concentrations in airborne particles (PM10) collected at urban sites in Boston, MA. Average Pt, Pd, Rh, and Os concentrations were 6.9 +/- 1.9, 8.1 +/- 1.8, 1.50 +/- 0.50, and 0.068 (-0.068 + 0.070) pg m(-3), respectively. Elevated Pt, Pd, and Rh concentrations are attributed to automobile catalysts, which use Pt, Pd, and Rh for the removal of pollutants from engine exhaust gas. An automobile catalyst source is supported by significant correlations between these elements and by a Pt/Rh similar to that in catalysts. Elevated Os concentrations are also believed to be the result of emission from automobile catalysts in which Os occurs as an impurity. The isotopic composition of Os (187Os/ 188Os) ranged from 0.30 to 2.90, indicating large variations in Os sources. Osmium has a predominantly anthropogenic origin at concentrations > 0.1 pg m(-3), whereas natural sources are more important at lower Os concentrations. Osmium isotopic composition also indicates that Pt, Pd, and Rh in Boston air are of almost exclusive anthropogenic origin, with a relatively small natural contribution. Our results indicate that scavenging by rain plays a major role in the atmospheric residence time and environmental fate of PGE.     

Decoupling Minimal Surface Metamaterial Properties Through Multi-Material Hyperbolic Tilings

Rapid advances in additive manufacturing have kindled widespread interest in the rational design of metamaterials with unique properties over the past decade. However, many applications require multi-physics metamaterials, where multiple properties are simultaneously optimized. This is challenging since different properties, such as mechanical and mass transport properties, typically impose competing requirements on the nano-/micro-/meso-architecture of metamaterials. Here, a parametric metamaterial design strategy that enables independent tuning of the effective permeability and elastic properties is proposed. Hyperbolic tiling theory is applied to devise simple templates, based on which triply periodic minimal surfaces (TPMS) are partitioned into hard and soft regions. Through computational analyses, it is demonstrated how the decoration of hard, soft, and void phases within the TPMS substantially enhances their permeability–elasticity property space and offers high tunability in the elastic properties and anisotropy at constant permeability. Also shown is that this permeability–elasticity balance is well captured using simple scaling laws. The proposed concept is demonstrated through multi-material additive manufacturing of representative specimens. The approach, which is generalizable to other designs, offers a route towards multi-physics metamaterials that need to simultaneously carry a load and enable mass transport, such as load-bearing heat exchangers or architected tissue-substituting meta-biomaterials.     

Rotating sample holder at low temperature

A low temperature rotary device (cryoturbine) for use in extended x-ray-absorption fine structure measurements in fluorescence mode has been designed and manufactured. The instrument works at a temperature close to liquid Nitrogen and can reach frequencies up to 100 Hz with good stability. The rotation speed is measured with a light-emitting diode driven in stroboscopic mode by a simple electronic circuit.     

Spatially homogeneous gelation in liquid composite molding

On‐line mixing of the resin with its curing agents prior to injection into a mold is a common industrial technique for fabricating composite parts. For vinyl‐ester resins that cure via free radical polymerization, the concentrations of retarder, accelerator, and initiator are pre‐selected and cannot be changed during the injection. Hence, the resin that enters the mold the earliest has cured longer than the resin that enters the mold later, since the gel time for the resin is the same, owing to the fixed ratio of the curing agents. This approach leads to inhomogeneous cure of the resin and consequently to longer residence time of the resin in the mold. It requires an additional 50 to 75 percent of the filling time before a part can be de‐molded. In this study, it is shown that by adjusting the concentration of curing agents during the injection, a more homogeneous gel time throughout the mold can be achieved. The time to de‐mold is reduced to 18‐24 percent of the filling time. Sensors that measure the conductivity of the resin were used to detect the location and monitor the cure of vinyl‐ester. This approach could be extended to other resin systems to control the spatial curing of the resin in the mold.     

Seeded Stage III glass dissolution behavior of a statistically designed glass matrix

The dissolution rate of some glasses accelerates after prolonged time spent at a slow, residual dissolution rate. This phenomenon is referred to as Stage III behavior. The acceleration in glass dissolution rate linked to Stage III behavior is significant and may be the most impactful behavior to long-term performance of glass in a repository. This work is aimed at understanding the effect of glass composition on Stage III behavior to add a level of technical defensibility to glass disposal. To this end, a set of 24 glass compositions were statistically designed, where eight glass components (SiO₂, B₂O₃, Al₂O₃, CaO, Na₂O, SnO₂, ZrO₂, and Others) have been independently varied in order to study the individual effects of each glass component. These glasses have been subjected to static dissolution tests at 90°C in deionized water and then seeded with zeolite Na-P2 28 days into the testing to induce Stage III behavior. The response of the glasses to the zeolite seeds fell into four primary types: (1) no response to seeds; (2) an immediate linear sustained acceleration in the rate; (3) an immediate linear acceleration in the rate followed by a decrease; and (4) a progressive acceleration in the rate that is concurrent with the addition of the seeds. The main glass components observed to influence these behaviors were CaO, Al₂O₃, B₂O₃, and ZrO₂, where (1) CaO influenced which glasses showed a Stage III response to seeds (high CaO: types 2, 3, and 4) or did not respond to seeds (low CaO: type 1), (2) Al₂O₃ and B₂O₃ influenced which glasses showed a sustainable Stage III response (high Al₂O₃: types 2 and 4) versus transitory response (low Al₂O₃ and high B₂O₃: type 3), and (3) ZrO₂ concentration influenced whether glasses showed a linear (high ZrO₂: type 2) versus progressive (low ZrO₂: type 4) response to seeds.     

Industrial-scale Malting Barley (Hordeum vulgare L.) Seed Disinfection by Fog of Ozonated Water Application

The aim of this study was to underscore that seed treatment by the fog of ozonated water constitutes a promising alternative tool, in terms of health and environmental gains, regarding traditional ozone treatment. In order to obtain a clear vision of this performance, the technology was implemented on an industrial scale (malting industry). Under an exposition of barley seeds to 9.8 ppm of dissolved ozone into water, our results showed a significant disinfection effect of 80% for Fusarium sp. and 70% for Aspergillus sp., but no effect was established on Alternaria sp.