Atomic-Scale 3D Structure of a Supported Pd Nanoparticle Revealed by Electron Tomography with Convolution Neural Network-Based Image Inpainting.

Electron tomography based on scanning transmission electron microscopy (STEM) is used to analyze 3D structures of metal nanoparticles on the atomic scale. However, in the case of supported metal nanoparticle catalysts, the supporting material may interfere with the 3D reconstruction of metal nanoparticles. In this study, a deep learning-based image inpainting method is applied to high-angle annular dark field (HAADF)-STEM images of a supported metal nanoparticle to predict and remove the background image of the support. The inpainting method can separate an 11 nm Pd nanoparticle from the θ-Al2 O3 support in HAADF-STEM images of the θ-Al2 O3 -supported Pd catalyst. 3D reconstruction of the extracted images of the Pd nanoparticle reveals that the Pd nanoparticle adopts a deformed structure of the cuboctahedron model particle, resulting in high index surfaces, which account for the high catalytic activity for methane combustion. Using the xyz coordinate of each Pd atom, the local Pd-Pd bond distance and its variance in a real supported Pd nanoparticle are visualized, showing large strain and disorder at the Pd-Al2 O3 interface. The results demonstrate that 3D atomic-scale analysis enables atomic structure-based understanding and design of supported metal catalysts.

Enhanced High Thermal Conductivity Cellulose Filaments via Hydrodynamic Focusing.

Nanocellulose is regarded as a green and renewable nanomaterial that has attracted increased attention. In this study, we demonstrate that nanocellulose materials can exhibit high thermal conductivity when their nanofibrils are highly aligned and bonded in the form of filaments. The thermal conductivity of individual filaments, consisting of highly aligned cellulose nanofibrils, fabricated by the flow-focusing method is measured in dried condition using a T-type measurement technique. The maximum thermal conductivity of the nanocellulose filaments obtained is 14.5 W/m-K, which is approximately five times higher than those of cellulose nanopaper and cellulose nanocrystals. Structural investigations suggest that the crystallinity of the filament remarkably influence their thermal conductivity. Smaller diameter filaments with higher crystallinity, that is, more internanofibril hydrogen bonds and less intrananofibril disorder, tend to have higher thermal conductivity. Temperature-dependence measurements also reveal that the filaments exhibit phonon transport at effective dimension between 2D and 3D.

Tuning 2D magnetism in Fe3+XGeTe2 films by element doping.

Two-dimensional (2D) ferromagnetic materials have been discovered with tunable magnetism and orbital-driven nodal-line features. Controlling the 2D magnetism in exfoliated nanoflakes via electric/magnetic fields enables a boosted Curie temperature (T C) or phase transitions. One of the challenges, however, is the realization of high T C 2D magnets that are tunable, robust and suitable for large scale fabrication. Here, we report molecular-beam epitaxy growth of wafer-scale Fe3+XGeTe2 films with T C above room temperature. By controlling the Fe composition in Fe3+XGeTe2, a continuously modulated T C in a broad range of 185-320 K has been achieved. This widely tunable T C is attributed to the doped interlayer Fe that provides a 40% enhancement around the optimal composition X = 2. We further fabricated magnetic tunneling junction device arrays that exhibit clear tunneling signals. Our results show an effective and reliable approach, i.e. element doping, to producing robust and tunable ferromagnetism beyond room temperature in a large-scale 2D Fe3+XGeTe2 fashion.

Inter-element miscibility driven stabilization of ordered pseudo-binary alloy.

An infinite number of crystal structures in a multicomponent alloy with a specific atomic ratio can be devised, although only thermodynamically-stable phases can be formed. Here, we experimentally show the first example of a layer-structured pseudo-binary alloy, theoretically called Z3-FePd3. This Z3 structure is achieved by adding a small amount of In, which is immiscible with Fe but miscible with Pd and consists of an alternate L10 (CuAu-type)-PdFePd trilayer and Pd-In ordered alloy monolayer along the c axis. First-principles calculations strongly support that the specific inter-element miscibility of In atoms stabilizes the thermodynamically-unstable Z3-FePd3 phase without significantly changing the original density of states of the Z3-FePd3 phase. Our results demonstrate that the specific inter-element miscibility can switch stable structures and manipulate the material nature with a slight composition change.

Highly Correlated Size and Composition of Pt/Au Alloy Nanoparticles via Magnetron Sputtering onto Liquid.

Pt/Au alloy nanoparticles (NPs) in a wide composition range have been synthesized by room-temperature simultaneous sputter deposition from two independent magnetron sources onto liquid PEG (MW = 600). The prepared NPs were alloyed with the face-centered cubic (fcc) structure. In addition, the particle sizes, composition, and shape are strongly correlated but can be tailored by an appropriate variation of the sputtering parameters. No individual particle but large agglomerates with partial alloy structure formed at Pt content of less than 16 atom %. Highly dispersed NPs with no agglomeration were observed in PEG when the quantity of Pt is more than 26 atom %. On the other hand, a small amount of Pt could terminate the agglomeration of Au when sputtering on the grids for transmission electron microscope observation. Our experiment and computer simulation carried out by two different methods indicate that the composition-dependent particle size of Pt/Au can be explained by the atomic concentration, formation energy of the cluster, and interaction between different metal atoms and the PEG molecule.

Preparation and Growth Mechanism of Pt/Cu Alloy Nanoparticles by Sputter Deposition onto a Liquid Polymer.

We use a green sputtering technique to deposit a Pt/Cu alloy target on liquid polyethylene glycol (PEG) to obtain well-dispersed and stable Pt29Cu71 alloy nanoparticles (NPs). The effects of sputtering current, rotation speed of the stirrer, sputtering time, sputtering period, and temperature of PEG on the particle size are studied systematically. Our key results demonstrate that the aggregation and growth of Pt/Cu alloy NPs occurred at the surface as well as inside the liquid polymer after the particles landed on the liquid surface. According to particle size analysis, a low sputtering current, high rotation speed for the stirrer, short sputtering period, and short sputtering time are found to be favorable for producing small-sized single crystalline alloy NPs. On the other hand, varying the temperature of the liquid PEG does not have any significant impact on the particle size. Thus, our findings shed light on controlling NP growth using the newly developed green sputtering deposition technique.

Synthesis of zero-valent iron nanoparticles via laser ablation in a formate ionic liquid under atmospheric conditions.

Transition metal nanoparticles (NPs) are promising materials for use as catalysts in many processes, although they are easily oxidized under ambient conditions. In this communication, a novel synthetic method is proposed for producing zero-valent iron (Fe) NPs by laser ablation under atmospheric conditions using the reducing properties of a formate-based ionic liquid solvent. The valence state of Fe was confirmed using X-ray absorption near edge structure (XANES) spectroscopy. The Fe NPs adopt a face centered cubic structure after synthesis, which gradually transforms to a body centered cubic structure after one month. The method can be extended to the synthesis of other transition metal NPs that are easily oxidized.

Influence of leg-length discrepancy on anterior acetabular coverage using false profile image.

BACKGROUND: Leg-length discrepancy (LLD) occurs commonly in patients with osteoarthritis (OA) of the hip. Although some investigators argue that LLD in a weight-bearing position may influence lateral acetabular coverage, there have been no reports on the influence of LLD on anterior acetabular coverage and the relationship between LLD and vertical center anterior margin (VCA) angle before and after LLD correction. Anterior acetabular coverage is an important index for diagnosis, treatment, and surgery for OA of the hip. Therefore, we investigated the influence of LLD in a weight-bearing position on VCA angle. METHODS: There were 154 patients with LLD in OA of the hip and 146 healthy individuals without LLD. The sole of the short-leg side in patients was adjusted with an acrylic plate, and the LLD revision value was calculated in the anteroposterior (AP) view in a weight-bearing position. Calculated revision value was applied to individuals and VCA angles in false profile images before and after correction was measured. For healthy individuals, we corrected the sole of the nonexamined side with an acrylic plate to artificially increase LLD and then measured VCA angles in false profile images before and after correction. RESULTS: Significant difference was found in VCA angles between before and after LLD correction in patients and healthy individuals (p < 0.05). Difference in VCA angles before and after LLD correction in both patients and health individuals highly correlated with LLD level in both short- and long-leg sides. CONCLUSIONS: This study clarified that LLD in a weight-bearing position influenced VCA angle. Results suggested that comparison of images before and after correction increases diagnostic accuracy. Assessing anterior acetabular coverage before and after LLD correction is valuable in evaluating the need for surgery, suitable correction of osteotomized acetabular fragments in periacetabular osteotomy, and determining acetabular cup angle in artificial joint replacement.

[Hip joint radiographic technique: radiographic technique for false profile view (a study of optimum foot position)].

PURPOSE: To establish a more effective false profile (FP) radiography standard via theoretical consideration of patients' non-inspection-side foot position. PROBLEM: Existing FP radiography admits to two difficulties: 1) A 65-degree pelvic rotation results in differing inter-femoral head distances in individual patients, and 2) the desired angle of rotation of the pelvis is difficult to maintain throughout the examination period. METHOD: The following investigations were performed in this study: 1) inter-femoral head distance using computed tomography (CT) images; 2) optimum outside rotation angle of the non-inspection side for standing comfort; and 3) optimum foot position of the non-inspection side. RESULTS: 1) CT examination revealed an average inter-femoral head distance of 28.7 mm in males and 40.3 mm in females, with a maximum distance of 57.5 mm and minimum distance of 44.1 mm. 2) Investigation established the optimum outside angle of rotation to be 60 degrees. 3) Investigation revealed that the optimum foot position requires that the patient's heel be retracted 3 cm along the axis created by a pelvic rotation of 65 degrees. CT was used to verify the accuracy of the FP view method. CT comparison revealed that X-rays are able to obtain a view quite similar in quality to that of CT. CONCLUSION: It is of utmost importance in FP radiography to establish the optimum foot position for a pelvic rotation value of 65 degrees.