Material Design Approach Research Articles

First-principles based machine learning study of oxygen evolution reactions of perovskite oxides using a surface center-environment feature model

Perovskite-type oxide ABO3 catalysts can be used to prepare inexpensive, efficient, durable, and environmentally friendly electrochemical energy conversion devices. The numerous combinatorial substitutions of perovskite oxides provide rich choices of candidates but pose a great challenge to examine all the possibilities both experimentally and computationally. Inspired by the data-driven materials design approach, we proposed a surface center-environment (SCE) feature model and developed first-principles based machine learning (ML) methods to predict the adsorption free energies of intermediate species (HO*, O*, and HOO*) on the surfaces of perovskite oxides and their overpotentials, critical to evaluating the catalytic performance of oxygen evolution reaction (OER). The SCE feature models contain the elementary properties of substitution elements and the structure information of the perovskite surfaces, demonstrated as an effective description of catalytic reactions on surface in ML models. The ML models predicted that the perovskite oxides adsorb the intermediate species most easily when B = Nb, Mo, Ta, W, and Os, and their overpotentials are low when B = Mn, Fe, Co, Ru, Rh, and Ir. This work demonstrated that the machine learning methods based on SCE features can be applied to describe surface chemical reactions and accelerate the screening for potential perovskite catalysts with target properties.

Cluster-formula-embedded machine learning for design of multicomponent \u03b2-Ti alloys with low Young\u2019s modulus

The present work formulated a materials design approach, a cluster-formula-embedded machine learning (ML) model, to search for body-centered-cubic (BCC) β-Ti alloys with low Young’s modulus (E) in the Ti–Mo–Nb–Zr–Sn–Ta system. The characteristic parameters, including the Mo equivalence and the cluster-formula approach, are implemented into the ML to ensure the accuracy of prediction, in which the former parameter represents the BCC-β structural stability, and the latter reflects the interactions among elements expressed with a composition formula. Both auxiliary gradient-boosting regression tree and genetic algorithm methods were adopted to deal with the optimization problem in the ML model. This cluster-formula-embedded ML can not only predict alloy property in the forward design, but also design and optimize alloy compositions with desired properties in multicomponent systems efficiently and accurately. By setting different objective functions, several new β-Ti alloys with either the lowest E (E = 48 GPa) or a specific E (E = 55 and 60 GPa) were predicted by ML and then validated by a series of experiments, including the microstructural characterization and mechanical measurements. It could be found that the experimentally obtained E of predicted alloys by ML could reach the desired objective E, which indicates that the cluster-formula-embedded ML model can make the prediction and optimization of composition and property more accurate, effective, and controllable.

Ultrahigh piezoelectricity in lead-free piezoceramics by synergistic design

Abstract Following increased environmental concerns on the toxicity of lead, the discovery of ultrahigh piezoelectricity in lead-free piezoelectric materials is critical for the substitution of commercial lead zirconate titanate (PZT) ceramics in numerous electronic devices. In this work, a synergistic design strategy is proposed to enhance the piezoelectricity in lead-free piezoelectric materials by flattening the Gibbs free energy density profile, via the coexistence of multiple phases and local structural heterogeneity. This strategic material design approach is based on first-principles calculations combined with Landau phenomenological theory and phase field simulations. Sustainable Stannum-doped BaTiO3 lead-free ferroelectric ceramics are prepared to validate our proposed mechanism, and a giant piezoelectric coefficient d33 > 1100 pC/N is achieved, being the highest value reported in lead-free piezoceramics. The mechanism and paradigm of the excellent piezoelectricity achieved here provides a feasible solution for replacing lead-based piezoelectrics by lead-free counterparts.

Research status of the rare and precious metals’ Materials Genome Initiative

The core philosophy of Materials Genome Initiative (MGI) is the transition of the way of new materials design from the traditional “trial-and-error” approach to the in-silico materials design approach which employs intensive computing and material informatics. In June 2011, President Barack Obama launched MGI alongside the Advanced Manufacturing Partnership to help businesses discover, develop and deploy new materials twice as fast. In this paper, the concept of rare and precious genome is presented first, followed by the progress of MGI. After that, we focus on the research status of the rare and precious metals’ MGI including the computational tools, the high-throughput experimental methodologies and the rare and precious metals database. We also introduce the application of MGI in the development of rare and precious metal materials, outline the remaining fundamental challenges and present an outlook on the future of the rare and precious metals’ MGI.

In Situ Observations of Molecular CO2 Interaction on SnS2 Thin Film for Gas-Phase Photocatalytic CO2 Reduction Activity

Among the several approaches, the gas phase photocatalytic conversion of CO2 to useful fuels with the help of renewable energy sources and water vapor has attracted widespread attention. In this system, the gas-solid interaction between a CO2 molecule and a solid catalyst surface is a crucial step. However, the adsorbate-catalyst surface interaction in the gas-phase of CO2 reduction system on the surface of semiconductor photocatalysts remains unaddressed.In this report, high-quality SnS2 thin film was prepared through a chemical vapor transport process followed by controlled carbon implantation to form C-SnS2. Our material design and characterization approaches, which involve in-situ observations enabled us to correlate the adsorbate-catalyst surface interactions and their implications on photocatalytic CO2 reduction. Using in-situ dark current and in-situ Raman spectroscopy, under different gas ambient conditions, we have observed that, the C-SnS2 surface exhibited a strong affinity towards CO2 molecule and higher photon to electron conversion efficiency under light illumination. In addition, the optimized carbon implanted SnS2 sample has demonstrated more than 108 times enhancement in the CO2 conversion efficiency and about 89% product selectivity towards CH4 formation. Additional information on the mechanism of interfacial charge transfer was obtained using angle-dependent XANES, X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) analysis.We anticipate that the adsorbate-catalyst surface interaction studies applied in this report can be extended to be used as a benchmark in design and material selection in the gas-phase CO2 photoreduction applications. We further expect that C-SnS2 with its promising photocatalytic performance and high affinity toward CO2 adsorption and activation; will inspire the development of new semiconductor photocatalysts by modifying it with metal or non-metal dopants towards CO2 conversion into useful products. The detail characterization and experimental results with the future perspective of this study will be presented.

A hyperbranched polymer with enhanced photorefractive effect at low and zero applied electric field

Organic photorefractive (PR) materials are widely applied in electro-optical technologies. However, most PR materials require a high external electric field to show PR effect, which would cause materials dielectric fatigue and electrical breakdown. It is significant to explore materials that demonstrate high PR effects under low and even zero applied electric field. In this work, through Suzuki polymerization, a hyperbranched conjugated polymeric PR materials is prepared to show high PR effects with coupling gain coefficients (Г values) of 86.3 cm−1 and 62.5 cm−1 at low applied electric field of 2.5 V μm−1 and even 0 V μm−1, respectively, which are superior to the performance of its linear analogue. These results verify the advantages of branched structure in producing high PR effect, providing a new approach for PR material design.

Macrophase-Separated Organic Ionic Plastic Crystals/PAMPS-Based Ionomer Electrolyte: A New Design Perspective for Flexible and Highly Conductive Solid-State Electrolytes.

A material design approach was taken for the preparation of an organic ionic plastic crystal (OIPC)-polymer electrolyte material that exhibited both good mechanical and transport properties. Previous attempts to form this type of electrolyte material resulted in the solvation of the OIPC by the ionomer and loss of the plastic crystal component. Here, we prepared, in situ, a macrophase-separated OIPC-polymer electrolyte system by adding lithium bis(fluorosulfonyl)imide (LiFSI) to a (PAMPS–N1222) ionomer. It was found that an optimal compositional window of 40–50 mol % LiFSI exists whereby the electrolyte conductivity suddenly increased 4 orders of magnitude while exhibiting elastic and flexible mechanical properties. The phase behavior and transport properties were studied using differential scanning calorimetry and 7Li and 19F solid-state nuclear magnetic resonance spectroscopy. This is the first example of a fabrication principle that lends itself to a wide range of promising OIPC and ionomeric materials. Subsequent studies are required to characterize and understand the morphology and conductive nature of these systems and their application as electrolyte materials.

Li/Mn-Rich Cathode Materials with Low-Cobalt Content and Core-Shell Particle Design for High-Energy Lithium Ion Batteries

Li/Mn-rich positive electrode materials are widely known for their high energy content, which exceeds that of current cathodes significantly. Their implementation in practical high-energy lithium ion batteries has to date been hindered by various technical challenges, most of all, their insufficient long-term charge/discharge cycling performance. Here, a new concept for designing core–shell (CS) materials for this class is introduced, which is based on cathode particles, which are specifically designed to have an anionic redox-rich core and a shell with reduced anionic redox. This material design approach aims to overcome the drawback of having the sensitive anionic redox at the electrolyte/active material interface, and, therefore, extenuating the phase degradation from layered- to spinel- or even rock salt-structure. In this work, the effect of a CS particle design with a Co-free, Mn-rich core and a Co-containing shell with lower Mn content is studied. The spherical cathode particles, produced by a Couette Taylor Flow Reactor, enable a superior electrochemical performance with excellent initial Coulombic efficiencies of 90%–95% and improved long-term cycling performances compared to the reference materials, consisting of the pure core or pure shell composition.

Progress in development of electrocatalyst for CO2 conversion to selective CO production

AbstractThe conversion of carbon dioxide (CO2) to valuable fuels and chemicals offers a new pathway for sustainable and clean carbon fixation. Recently, the focus has been on electrochemical CO2 reduction on heterogeneous electrode catalysts, leading to remarkable achievements in the reaction performance. To date, CO2 to carbon monoxide (CO) conversion is considered as the most promising candidate reaction for the industrial market, owing to its high efficiency and reasonable technoeconomic feasibility. Moreover, CO has been proposed as a key intermediate species for further reduced hydrocarbons, which can pave the way for various fuel production. This study sets out to describe recent progress on the electrochemical CO2 reduction to CO in a heterogeneously catalyzed system. The review includes understanding of the catalytic material employed and engineering strategies implemented by adjusting the binding energy of key adsorbates. These material design approaches, such as nanostructuring, alloying, doping, and so forth, have pioneered breakouts in the intrinsic catalytic nature of transition metal elements. Moreover, recent advances in systematic design are summarized, with focus on practical industrial applications. Finally, perspectives on the design of electrocatalyst materials for CO production by electrochemical CO2 reduction are presented.

Highly cooperative fluorescence switching of self-assembled squaraine dye at tunable threshold temperatures using thermosensitive nanovesicles for optical sensing and imaging

Thermosensitive fluorescent dyes can convert thermal signals into optical signals as a molecular nanoprobe. These nanoprobes are playing an increasingly important part in optical temperature sensing and imaging at the nano- and microscale. However, the ability of a fluorescent dye itself has sensitivity and accuracy limitations. Here we present a molecular strategy based on self-assembly to overcome such limitations. We found that thermosensitive nanovesicles composed of lipids and a unique fluorescent dye exhibit fluorescence switching characteristics at a threshold temperature. The switch is rapid and reversible and has a high signal to background ratio (>60), and is also highly sensitive to temperature (10–22%/°C) around the threshold value. Furthermore, the threshold temperature at which fluorescence switching is induced, can be tuned according to the phase transition temperature of the lipid bilayer membrane forming the nanovesicles. Spectroscopic analysis indicated that the fluorescence switching is induced by the aggregation-caused quenching and disaggregation-induced emission of the fluorescent dye in a cooperative response to the thermotropic phase transition of the membrane. This mechanism presents a useful approach for chemical and material design to develop fluorescent nanomaterials with superior fluorescence sensitivity to thermal signals for optical temperature sensing and imaging at the nano- and microscales.

Composition‐induced non‐ergodic–ergodic transition and electrocaloric evolution in Pb 1−1.5 x La x Zr 0.8 Ti 0.2 O 3 relaxor ferroelectric ceramics

Relaxor ferroelectrics, with polar nanoregions (PNRs), are good candidates for electrocaloric (EC) refrigeration. This study investigates the EC performance of the Pb1−1.5x La x Zr0.8Ti0.2O3 relaxor ferroelectric ceramics by the direct measurement using a modified differential scanning calorimeter. All the ceramics exhibit pure perovskite phase with a dense microstructure. The results indicate that the increasing La substitution strengthens the relaxor behaviour, promotes the transition from non-ergodic to ergodic state, and enhances the thermal stability of EC property (instability η < 16% within 0–140°C for x = 0.09). While the EC peak widens and shifts to lower temperatures, the peak value decreases from ΔT max = 0.98 K (@140°C) for x = 0.06 to ΔT max = 0.25 K (@40°C) for x = 0.09 under an electric field of 40 kV/cm. Moreover, the ceramics with x = 0.07, near the non-ergodic–ergodic state boundary, show the optimised room temperature EC performance, i.e. ΔT = 0.41 K (@20°C) and η < 20% within a wide temperature range of 0–80°C. This work provides an effective material design approach for EC refrigeration in different application conditions.

Investigation of Geometric Landscape and Structure-Property Relations for Colloidal Superstructures Using Genetic Algorithm.

Over the past two decades, colloidal particles with a variety of shapes, sizes, and compositions have been synthesized and characterized successfully. One of the most important applications for colloidal building blocks is to engineer functional structures as mechanical, electrical, and optical metamaterials. However, complex interaction dynamics between the building blocks as well as sophisticated structure-property relationships make it challenging to design structures with predictable target properties. In this paper, we implement an inverse material design framework using Genetic Algorithm (GA)-based techniques to streamline the design of colloidal structures based on target properties. We investigate spherical particles as well as colloidal molecules of different sizes and shapes and evaluate a Geometric Landscape Accessibility parameter that identifies the size of feasible domains within the geometric phase space of each structure. Considering target photonic properties, our GA-assisted framework is further utilized to identify sets of building blocks and structures that lead to various target values for the size of the photonic band gaps. The proposed framework in this study will provide new insight for predictive computational material design approaches and help establish more efficient ways of understanding structure-property relations in sub-micrometer-scale materials.

Ionic Hydrogel for Accelerated Dopamine Delivery via Retrodialysis.

Local drug delivery directly to the source of a given pathology using retrodialysis is a promising approach to treating otherwise untreatable diseases. As the primary material component in retrodialysis, the semipermeable membrane represents a critical point for innovation. This work presents a new ionic hydrogel based on polyethylene glycol and acrylate with dopamine counterions. The ionic hydrogel membrane is shown to be a promising material for controlled diffusive delivery of dopamine. The ionic nature of the membrane accelerates uptake of cationic species compared to a nonionic membrane of otherwise similar composition. It is demonstrated that the increased uptake of cations can be exploited to confer an accelerated transport of cationic species between reservoirs as is desired in retrodialysis applications. This effect is shown to enable nearly 10-fold increases in drug delivery rates from low concentration solutions. The processability of the membrane is found to allow for integration with microfabricated devices which will in turn accelerate adaptation into both existing and emerging device modalities. It is anticipated that a similar materials design approach may be broadly applied to a variety of cationic and anionic compounds for drug delivery applications ranging from neurological disorders to cancer.

Design and Development of Hybrid Al2O3 Based Composites with Toughening and Self-Lubricating Second-Phase Inclusions.

Polycrystalline ceramics, such as alumina (Al2O3), are brittle and they generally wear by fracture mechanism, which limits their potential in tribological applications. In the present work, computational design tools are used to develop hybrid Al2O3 composites reinforced with best combinations of toughening and self-lubricating second-phase particles for cutting tool inserts in dry machining applications. A mean-field homogenization approach and J-integral based fracture toughness models are employed to predict the effective structural properties (such as elastic modulus and fracture toughness) and related to the intrinsic attributes of second- phase inclusions in Al2O3 matrix. Silicon carbide (SiC), boron nitride (cBN and hBN), zirconia (ZrO2), graphite, titanium dioxide (TiO2), and titanium carbide (TiC) were found the most suitable candidates to be added in Al2O3 matrix as individual or hybrid combinations. A series of samples including standalone Al2O3, single inclusion composites (Al2O3/SiC, Al2O3/cBN) and hybrid composites (Al2O3/SiC/cBN, Al2O3/SiC/TiO2 and Al2O3/SiC/graphite) are sintered by Spark Plasma Sintering (SPS) for validation purpose. Properties of the sintered composites are measured and compared with the proposed computational material design. Composition and phase transformation of the sintered samples are studied using X-ray diffraction (XRD) and Raman spectroscopy, while their morphology is studied using Field Emission Scanning Electron Microscope (FESEM). The presented nontraditional material design approach is found to significantly reduce experimental time and cost of materials in developing toughened and anti-friction ceramic composites.

3D-printed polymer composites with acoustically assembled multidimensional filler networks for accelerated heat dissipation

Polymer composites containing thermally conductive fillers show great promise in solving the overheating issue which is critical for electronic devices. Recent successes in developing functional polymer composites rely on the excellent filler property and heavy loading. Yet the intensive filler loading leads to challenges in manufacturing and composite properties. This study reports an alternative method for functional particle-polymer composite design and fabrication: instead of heavy loading, a small amount of filler composes highly concentrated multidimensional network functioning as active paths for heat dissipation in the polymer matrix. A novel 3D printing technique named acoustic field-assisted projection stereolithography realizes the fabrication of such composites. The local filler weight ratio in the network is > 7 times of the feedstock filler loading. With the same feedstock, the patterned composite exhibits >10 times higher efficiency in heat dissipation, compared to the uniform composite. With the same amount of fillers embedded, the patterned composite accelerates the heat dissipation twice than the uniform composite. Moreover, 3D filler network outperforms 2D network, showing that the higher network dimension is conducive to multidirectional heat transfer. With a low filler consumption while higher design flexibility, this new composite material design and manufacturing approach overcomes restriction caused by filler loading.

First Principles Investigation of Grain Boundary Effects in Perovskite-Type Lithium Lanthanum Titanate Solid Electrolyte

Lithium lanthanum titanate (LLTO) is considered a particularly promising candidate for use as an electrolyte in all-solid-state lithium ion batteries due its good electrochemical stability and high ionic conductivity. However, measured values for the ionic conductivity of LLTO fall far below theoretical predictions, an incongruity which has been attributed to the presence of grain boundaries. Furthermore, recent experimental work has shown that lithium dendrite growth occurs along the grain boundaries in LLTO. While experimental studies have been able to reveal the detailed microstructure of polycrystalline LLTO, but little effort has been made to identify the fundamental mechanisms at work within the grain boundaries which lead to to suppressed ionic conductivity and Li dendrite growth. Using ab-initio calculations, we examine the electronic character of LLTO grain boundaries and investigate the impact of the defect states on ion transport and dendrite formation. Based on a fundamental understanding of the atomic and electronic character of LLTO grain boundaries, material design approaches are proposed to mitigate the impact of grain boundary behavior and improve the viability of LLTO as a practical solid electrolyte. This work was supported by the International Energy Joint R&D Program (No. 20168510011350) of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Ministry of Knowledge Economy, Korean government. This work is also supported by the L&F Co.’s World Class 300 Project of the Korea Institute of Advancement of Technology (KIAT) funded by the Ministry of Trade, industry and Energy (No.S2483103).

Hydrophobic metal-organic frameworks: Potential toward emerging applications

Metal-organic frameworks, popularly known as MOFs, have come of age—thanks to custom-built design principles enabling them to serve a myriad of task-specific applications. In an era where &amp;gt;6000 new MOFs are annually published, driven by academic research, a new generation of MOFs that can find use in niche markets is on the rise. One of the foremost challenges that plague the translation of MOFs into materials suited for commercialization is their water-influenced degradation, largely accountable to hydrolytic instability and the ubiquity of water. Hydrophobic MOFs offer one of the most promising solutions which can enable these porous materials to leverage their functionalization guided properties even under extreme humid conditions, a criterion that application-ready materials should necessarily serve. In this contribution, our discussion focuses on the state-of-the-art hydrophobic MOFs and MOF-derived composites. Outlining a brief overview of the structure-property correlation aspects in each of these promising hydrophobic MOFs with little or no influence exhibited to water and/or humidity, a future outlook is put forward to enable potentially better design strategies leading to futuristic MOFs tolerant to water/moisture. Concise premise of this review allows us to limit our discussion to the design principles in action behind the most hydrophobic MOFs/derived composites reported thus far and to discuss their prime applications viz., oil/water separation inclusive of self-cleaning, hydrocarbon separation, and tackling marine oil spillage. When synergized, such improved porous material design approaches lean toward a greener environment of tomorrow.

Multi-property cellular material design approach based on the mechanical behaviour analysis of the reinforced lattice structure

Lattice structures have advantages such as energy absorption and heat transfer; however, they can often suffer failure because of stress distribution and lack of stiffness. A spherical-node-body-centred-cubic (SNBCC) structure was developed to reduce the stress concentration and improve the stiffness. The relative density, surface area, and equivalent modulus of the SNBCC structure were studied, and a method to select suitable parameters was developed. The results showed that the prediction errors of the theoretical relative density and surface area were both <1.00% compared with that of the CAD model. The theoretical modulus's prediction error was approximately 10.00% compared with that of the finite element analysis. Compared with the BCC structure, the relative density of the SNBCC structure only increased from 1.00% to 7.00%, the stress concentration reduced from 10.00% to 30.00%, and the stiffness increased from 5.00% to 58.10%, when the ratio of the strut diameter to the unit cell length was within 0.02–0.10. The projection approach for the lattice structure's multi-property design was applied. If a solid material's modulus is 200.00 GPa, the design range of the relative density and the equivalent modulus can be within 0.0021–0.1197 and 0.10 MPa–1.00 GPa respectively.

Towel-like composite: Edge-rich MoS2 nanosheets oriented anchored on curly N-Doped graphene for high-performance lithium and sodium storage

Molybdenum disulfide (MoS2) is a promising candidate for high-performance electrodes of lithium ion batteries (LIBs) and sodium ion batteries (SIBs). In this work, we propose an integrated towel-like structure comprising edge-rich, interlayer-expanded, and oxygen-incorporated MoS2 nanosheets oriented anchored on curly N-doped graphene (MS@N-G). The heterogeneous interfaces are connected via chemical bonds, which provide high-speed electronic transport and improve the structural stability of the hybrid materials. The designed structure delivers excellent rate capability of 461 mAh g−1 at 2000 mA g−1 for LIBs and 350 mAh g−1 at 1000 mA g−1 for SIBs, and long lifespan performance with 675 mAh g−1 at 500 mA g−1 after 450 cycles for LIBs and 396 mAh g−1 at 500 mA g−1 after 140 cycles for SIBs. This study reveals that the fundamental approach to improve the electrochemical performance of MoS2 on the electrode level is building a robust connection between the MoS2 and conductive matrix and optimizing the electron conduction across the interfaces. The materials design approach and synthesize procedure could be applied more broadly to high-performance energy storage electrode materials.

Electron engineering of metallic multiferroic polarons in epitaxial BaTiO3

The coexistence of ferroelectricity, conductivity, and magnetism in a single-phase material has attracted considerable attention due to fundamental interest and tremendous technological potential. However, their mutually exclusive mechanisms hinder the discovery of multifunctional conducting multiferroics. Here, we propose a new material design approach for electron engineering to enable these conflicting properties to coexist. We use first principles calculations to demonstrate that appropriate mechanical strain can turn the excess electrons in doped BaTiO3 from a free-carrier configuration to a localized polaronic state by modulating the electron–phonon coupling. The resulting localized spin-polarized electron survives the host ferroelectricity and consequently manifests as a multiferroic polaron. The multiferroic properties coexist with the electronic conductivity arising from the high-hopping mobility of the polaron, which enables the doped epitaxial BaTiO3 to act as a multiferroic conducting material. This mechanical control over the electron configuration is a potential path toward unusual coexisting properties.