Faceted Morphology Research Articles

Classification of the Os Calcis Subtalar Morphology in Symptomatic Flexible Pediatric Pes Planus Deformity Using Weightbearing CT and Distance Mapping.

The etiology of symptomatic pediatric pes planus (PP) deformity is unclear. Reduced os calcis subtalar joint (OCST) anterior facet morphology has been suggested to result in less support to the talar head and a higher propensity to develop PP deformity. Weightbearing computed tomography (WBCT) and distance mapping (DM) offer new opportunities to investigate PP deformity in general and the OCST specifically. The purpose of this study is to investigate the OCST morphology using DM and to classify PP subtalar subtypes with DM using Bruckner's A-D classification system. Forty feet in 25 patients in a national referral center were evaluated for symptomatic PP deformity that failed nonoperative treatment. A WBCT scan was performed as part of the preoperative evaluation. Visualization of the distance distribution between the articulating surfaces of the subtalar joint was based on a DM technique. Intra- and interobserver agreement of the subtalar morphology was assessed using Bruckner's classification system. The mean age was 10.7 ± 1.4 years. The following mean ± SD and median ± ranges were semiautomatically measured for this group: Meary angle -21 ± 8, calcaneal inclination 15 ± 4 degrees, talar coverage angle 39 (range 32.6-49) degrees, and hindfoot moment-arm 16 ± 5 mm. Classifying subtalar morphology using DM yielded an excellent intra- and interobserver agreement. The individual percentages of each individual subtype were calculated: type A 5%, type B 48%, type C 4%, and type D in 44%. This study demonstrated excellent intraobserver and interobserver agreement in classifying the OCST using DM. A higher prevalence of types B and D was observed compared to types A and C in this PP cohort. Level III, retrospective study.

Influence of heat input on the evolution of δ-ferrite grain morphology of SS308L fabricated using WAAM-CMT

Wire-arc additive manufacturing (WAAM) is acquiring impetus for fabricating medium-complexity and large metallic components owing to its high material deposition with faster building rates. Austenitic stainless steels are commonly used among the numerous materials processed by WAAM and microstructural study of single walled components has been widely researched in the past. In this paper, manual cold metal transfer (CMT) welding is used to produce WAAM samples of SS308L austenitic stainless steel with SS304 as a substrate. Detailed microstructural studies with grain morphology of δ-ferrite based on heat input at various layers fabricated using WAAM-CMT are mainly explored. Results showed that the concentration of γ-austenite drops as heat input increases, but δ-ferrite and micro-inclusions increase. Within δ-ferrite, lathy ferrite morphology evolves into faceted morphology while vermicular evolves into a globular (spheroidized) ferrite morphology as heat input increases. The grain morphology pattern repeats itself for each layer as moving along the building direction, resulting in a repetitive heterogenous grain morphology with nearly identical chemical compositions.

Enhanced metal exsolution at the non-polar (001) surfaces of multi-faceted epitaxial thin films

Metal exsolution is a dynamic process driven under a reducing atmosphere and at elevated temperatures that results in the self-assembly of nanoparticles at the surface of complex perovskite catalysts. The nanoparticle characteristics of metal exsolution catalysts can be subject to considerable inhomogeneity, and the anisotropic surface properties of ceramic oxides have been identified to have a major influence on the exsolution behavior. We systematically reveal the orientation-dependent anisotropy of the exsolution behavior of Ni in SrTi0.9Nb0.05Ni0.05O3−δ using multi-faceted epitaxial thin films that represent a material system with properties in between functional ceramics and single-crystalline perovskite thin film model systems. Using an approach of combined orientation mapping and surface imaging we study the exsolution behavior with particular focus on the initial exsolution response, i.e. after short annealing times. We find orientation-specific variations in the surface morphology of the thin film facets. In the as-prepared state, surface reconstructions cause the formation of patterned surface structures for all thin film facets apart from (001) surfaces, which exhibit a plain surface morphology as well as an enhanced exsolution response. Surface reconstructions and their inherent energy landscape may hence cause an additional energy barrier for the exsolution reaction that results in orientation-dependent differences in the exsolution kinetics.

Precipitation sequence in Al-Sc-Zr alloys revisited

Sc and Zr additions to Al provide significant strengthening through the formation of Al3(Sc,Zr) L12 dispersoids. Fe impurities are always present in commercial Al alloys and the effect of these impurities on precipitation mechanisms in Al-Sc-Zr alloys remain poorly understood. This is particularly relevant when considering recycled aluminium as recycling results in the build-up of impurities. We used a combination of resistivity and thermo-electric power (TEP) measurements to monitor the evolution of solid solution during ageing of an Al-Sc, Al-Zr and Al-Sc-Zr alloy. Sc first comes out of solution to form Al3Sc dispersoids, followed by Zr to form Al3Zr. A range of Al3Sc-core/Al3Zr-shell faceted morphologies were observed with high angular annular dark field scanning transmission electron microscopy (HAADF-STEM). The presence of a new class of Fe-rich plate-like precipitates in the {100}Al was revealed via HAADF-STEM. The ordered positions of the precipitate and matrix reflections in the selected area diffraction pattern and in high-resolution TEM images reveal that these precipitates display a multi-layered structure. The centre of the plates is pseudo-icosahedral with apparent five-fold symmetry, and is rich in Fe. The outside layer has a L12 structure and is rich in Sc and Zr. The layered structure allows complete coherency with the aluminium matrix. These precipitates are highly anisotropic with a thickness of 5-10 nm and a length up to ∼1000 nm. This is the first report of the formation of this type of coherent pseudo-icosahedral precipitates in isothermal conditions which is named the D-phase.

Ge Microcrystals Photedetectors with Enhanced Infrared Responsivity

he direct epitaxial growth of germanium on silicon (Ge-on-Si) has fostered the development of near infrared detectors for telecom and imaging applications [1]. The long wavelength responsivity of these devices is limited to approximately 1550 nm corresponding to the direct energy gap of Ge EgΓ= 0.8 eV. Indeed, the absorption coefficient at the indirect gap EgL= 0.66 eV (λ≈1800 nm) is roughly two orders of magnitudes lower than that above the direct gap threshold. A sizable absorption within the 1550-1800 nm windows would, therefore, require exceedingly thick epilayers leading to wafer bowing and crack formation. An extended infrared absorption would, however, be beneficial for imaging applications since long wavelength radiation is less affected by Rayleigh and Mie scattering limiting visibility in fog and dusty conditions.A viable route to enhance the responsivity of Gen-on-Si photodetectors in the 1550-1800 nm region might be exploiting the micro-structuring of the absorbing layer to increase the effective volume of interaction between light and matter.In this work we report on a new type of detector, obtained from Ge micro-crystals epitaxially grown on a patterned Si substrate [2]. The faceted morphology and relatively high aspect ratio of the microcrystals is seen to enhance the detector responsivity in the wavelength region comprised between the direct (λ≈1550 nm) and indirect (λ≈1800 nm) gap of Ge, as compared to conventional planar devices.The epitaxial growth has been performed by means of Low-Energy Plasma-Enhanced CVD (LEPECVD). Microcrystal formation is based on the self-assembly of Ge crystals on a Si substrate, deeply patterned by optical lithography and reactive ion etching. 3D microcrystals, several micrometer tall and characterized by a limited lateral expansion, are obtained by using optimized growth parameters. Due to crystal faceting, light trapping effects are expected to take place within the microcrystals leading to increased in the fraction of absorbed light when compared to conventional epitaxial layers.Modelling of the near-IR absorption properties of the Ge-on-Si micro-crystals, and of conventional epilayer used as a reference,has been performed by finite difference time domain (FDTD) simulations. The ratio between the fraction of absorbed power of an array of Ge-on-Si micro-crystals and a planar Ge-on-Si epilayer is estimated to be always higher than one, with a factor of two increase in the spectral region between the direct and indirect gap (λ≈1550-1800 nm).Ge microcrystals photodetectors have been fabricated using graphene as a transparent top contact (see Fig. 1). A confocal microscope with a supercontinuum laser source (1300 - 1800 nm), has been used to obtain the photodetector responsivity. The spot size was smaller than the patterned area (100 μm x 100 μm) thus enabling the illumination of a few Ge-on-Si micro-crystals. The photocurrent measurements experimentally confirm the enhanced absorption in the 1550-1800 nm spectral region [4] with a responsivity exceeding, by a factor of seven, that of a reference conventional Ge-on-Si photodiode at 1700 nm.These results pave the way to a new class of photodetectors, exploiting light trapping phenomena in self assembled semiconductors microstructures. J. Michel, J. Liu, and L. C. Kimerling, High-performance Ge-on-Si photodetectors, Nat. Photonics 4, 527–534, (2010)C. V. Falub et al., Scaling Hetero-Epitaxy from Layers to Three-Dimensional Crystals, Science (80). 1330–1334, (2012).M. Albani et al. Faceting of Si and Ge crystals grown on deeply patterned Si substrates in the kinetic regime: phase-field modelling and experiments, Scientific Reports 11, 18825 (2021)V. Falcone et al., Graphene/Ge microcrystal photodetectors with enhanced infrared responsivity, APL Photonics 7, 046106 (2022) Figure 1

Study of morphological pattern of the talar articular facets in dry human calcanei and its clinical implications

Background: The calcaneum is longest and largest of all the tarsal bone. Morphology of the talar articular facets of calcanei is important for anatomy with respect to diagnosis and treatment of the injuries related to foot. Aims: This study was done to understand the variation in the morphology of talar articular facets on the superior surface of human calcanei and to study various shapes of these facets . Methods: 138 of adult dry calcanei 86 of right side and 52 of left side of unknown gender were taken from the museum of Department of Anatomy of Rohilkhand Medical College and Hospital, Bareilly and LBKMCH,Saharsa and evaluated one by one. Result: PatternI was 69.5% of the studied bones, Pattern II and Pattern III were 4.3% each, Pattern IV was 21.7%, Pattern V was not found. The anterior and middle articular facets were mostly oval in shape and that of posterior articular facet was oval and convex. The calcaneal length was recorded with the mean and SD of 6.9 ± 0. 65cms (left side) and 6.9 ± 0. 9cm (right side). The width was 4.0 ± 0.38 cm (left) ,4.1 ± 0.3 cm (right).

Synthesis, Physical Properties and Electrocatalytic Performance of Nickel Phosphides for Hydrogen Evolution Reaction of Water Electrolysis.

Nickel phosphides have been investigated as an alternative to noble metals and have emerged as potential catalysts that can efficiently catalyze the hydrogen evolution reaction (HER). However, the impacts of facet morphology and crystal structure of the nickel phosphides on their catalytic reactivity have not been systematically investigated. Herein, nickel phosphides with different crystalline states were prepared through a facile calcination treatment. It was found that the calcination treatment had important effects on the phase compositions, morphologies, and crystallinity of nickel phosphides, which are closely related to their HER activity. Generally, the crystallized Ni-P catalysts exhibited faster kinetics than the amorphous Ni-P. In particular, the Ni-P 300 showed remarkable HER performance with of ca. 65 mV, along with a very low Tafel slope of ca. 44 mV dec−1 due to the increased catalytically active sites. Furthermore, the Ni-P 300 exhibited negligible decay during the 140 h galvanostatic electrolysis, showing better catalytic stability than the commercial Pt/C catalyst. Compared with the amorphous Ni-P, the boosted HER activity of the Ni-P 300 could benefit from the mixed nanocrystalline Ni2P and Ni3P, which could contribute to the Hads adsorption/desorption abilities and helped provide more activity sites, promoting the HER performance.

Morphological design of occlusal wear facets for the mandibular first molar crown using different bite registration methods.

To compare the accuracy of occlusal wear facet morphology designed using different bite registration methods for mandibular first molar crowns. The posterior teeth and intraoral intercuspal occlusions of 12 participants were scanned. The abutment shape of the mandibular first molars for complete crowns was virtually designed, and the anatomic coping design method was used to design crowns. In the anatomic coping design, digital wax patterns were constructed by elevating the wear facets on the original surface of the first molars and then adjusting the facets with 2 types of virtual occlusions determined by buccal bite registration (BBR) or segmented tooth registration (STR) methods, where the displacement of teeth under bite force was considered (STR) or not (BBR). The occlusal distance between the original wear facets and the antagonists as well as 3D deviations between the facets on the designed crowns and on the surfaces of the original teeth were measured. Paired-samples t-test was used to analyze the results (α = 0.05). Regarding occlusal distance, the mean 3D deviation and the root mean square (RMS) values of BBR were greater than those of the STR groups (p < 0.001 and p = 0.008). The mean 3D deviations of the crowns of the BBR and STR groups were 0.19 ±0.04 mm and 0.14 ±0.06 mm, respectively and the RMS values were 0.22 ±0.03 mm and 0.18 ±0.04 mm (p < 0.001), respectively. The morphology of occlusal wear facets of mandibular first molar crowns designed with the occlusion constructed using the segmented tooth registration method are more coincident with the original morphology.

Two-type classification system for femoral trochlear dysplasia in recurrent patellar instability based on three-dimensional morphology.

Radiographic and two-dimensional (2D) CT/MRI analysis of femoral trochlear dysplasia play a significant role in surgical decision-making for recurrent patellar instability. However, the three-dimensional morphology of dysplastic trochlea is rarely studied due to the limitations of conventional imaging modalities. This study aimed to (1) develop a 3D morphological classification for trochlear dysplasia based on the concavity of the trochlear groove and (2) analyze the interrater reliability of the classification system. The 3D trochleae of 132 knees with trochlear dysplasia and recurrent patellar instability were reconstructed using CT scan data and classified using the innovative classification criteria between January 2016 and June 2020. A concave trochlear sulcus with sloped medial and lateral trochlear facets was classified as Type I trochlea. The trochlear groove with no concavity is classified as Type II. Furthermore, in Type II, the trochlea with the elevated trochlear floor at the proximal part was identified as IIa and the trochlea with the hypoplastic trochlear facets as IIb. The intra- and inter-rater reliability was examined using kappa (κ) statistics. The 3D classification system showed substantial intra-rater agreement and moderate interrater agreement (0.581 ~ 0.772). The intra- and interrater agreement of Dejour's four-grade classification was fair-to-moderate (0.332 ~ 0.633). Eighty-one trochleae with concave trochlear sulcus were classified as Type I, and fifty-one without concavity as Type II. Twenty-five non-concave trochleae were classified as type IIa due to the elevated trochlear floor and 26 trochleae into IIb with the hypoplasia of trochlear facets. This study developed a 3D classification system to classify trochlear dysplasia according to trochlear concavity and morphology of the trochlear facets. On CT/MRI scans or 3D reconstructions, the interpretation of features of dysplastic trochleae may vary, especially for the flat and convex trochleae. The novel system provides morphological evidence for when to consider trochleoplasty according to the different types of trochlear sulcus.

Graphene/Ge microcrystal photodetectors with enhanced infrared responsivity

We report on the electrical and optical properties of microcrystal arrays obtained by depositing Ge on a deeply patterned Si substrate. Finite difference time domain simulations indicate that the faceted morphology and high refractive index of Ge microcrystals lead to strong light trapping effects, enhancing infrared light absorption in the spectral window between the direct and indirect absorption edge of Ge (≈1550–1800 nm). This is experimentally confirmed by fabricating microcrystal-based Ge-on-Si photodiodes employing graphene as a top transparent contact. In these devices, the ratio between the responsivities at 1550 and 1700 nm is more than ten times larger than that of photodiodes based on conventional Ge-on-Si epilayers.

The role of chelating agent on the structure and up-conversion property of NaLuF4:Yb,Tm as security ink phosphor

Purpose This study aims to investigate the effect of trisodium nitrilotriacetic acid (NTA) on the physical and luminescence emission properties of NaLuF4:Yb, Tm Upconversion (UC) particles and compared with trisodium citrate (CA). Upconversion materials have been remarkably considered in many applications in the past decades. However, the morphology of the UC particles affects their emission properties, depending on the synthesis situation. Design/methodology/approach The UC particles were synthesized by the hydrothermal method. Properties such as crystal phase, particle morphology, particle size, smoothness and uniformity of particle surface and their emission intensity in the UV–Vis region were studied. Findings Observations showed that pH is an essential factor in determining the crystalline phase. In addition, quality factors affect the morphology, particle size and surface smoothness of crystalline facets. It was also found that the UC particles synthesized in the presence of trisodium NTA have a much higher emission intensity than those synthesized in the presence of CA. The use of UC particles in security inks to maintain the brand was also investigated. Originality/value To the best of the authors’ knowledge, for the first time, the effect of trisodium NTA as a chelating agent was investigated on morphology and UC intensity of NaLuF4:Yb,Tm phosphor.

Scalable Gas Diffusion Electrode Fabrication for Electrochemical CO2 Reduction Using Physical Vapor Deposition Methods.

Electrochemical CO2 reduction (ECR) promises the replacement of fossil fuels as the source of feedstock chemicals and seasonal storage of renewable energy. While much progress has been made in catalyst development and electrochemical reactor design, few studies have addressed the effect of catalyst integration on device performance. Using a microfluidic gas diffusion electrolyzer, we systematically studied the effect of thickness and the morphology of electron beam (EB) and magnetron-sputtered (MS) Cu catalyst coatings on ECR performance. We observed that EB-Cu outperforms MS-Cu in current density, selectivity, and energy efficiency, with 400 nm thick catalyst coatings performing the best. The superior performance of EB-Cu catalysts is assigned to their faceted surface morphology and sharper Cu/gas diffusion layer interface, which increases their hydrophobicity. Tests in a large-scale zero-gap electrolyzer yielded similar product selectivity distributions with an ethylene Faradaic efficiency of 39% at 200 mA/cm2, demonstrating the scalability for industrial ECR applications.

A morphologic and morphometric study of articular facets of Patella

Background: The patella plays a major role in flexion and extension of the knee. The patella morphology can be a predisposing factor in patella instability. The congruency between the patella and femur affects the kinematics of the patellofemoral joint, contact mechanics of the patellar cartilage, and strain in the underlying bone, whereby higher stresses and strains potentially contribute to cartilage wear and anterior knee pain. Aim and Objective: The present study was conducted to assess the morphology of facets of patella. Materials and Methods: The present study was conducted to assess the morphology of facets of patella. Ninety-six patella of unknown sex from bone store of Department of Anatomy were included in the study. The patellar morphology and morphometry were investigated. Statistical analysis was performed using the SPSS (v 12.01) software package (SPSS Inc., Chicago, Illinois). Statistical significance was set at P &lt; 0.05. Results: In the present study; 96 patella of unknown sex from bone store of Department of Anatomy were included in the study. The mean size of the right lateral facet was 23.34 mm and left lateral facet patella was 23.06. P value was non-significant. The shape of lateral facet was concave in 93.9% in the left patella and 100% in the right patella. The shape of lateral facet was flat in 6.1% in the left patella and 0% in the right patella. The mean size of the right medial facet was 17.68 mm and left medial facet patella was 17.39 mm. P value was nonsignificant. The shape of medial facet was concave in 2% in the left patella and 10.6% in the right patella. The shape of medial facet was convex in 69.4% in the left patella and 61.7% in the right patella. The shape of medial facet was flat in 28.6% in the left patella and 27.6% in the right patella. P value was non-significant. Conclusion: The present study concluded that the mean size of the right lateral facet was more left lateral facet patella. The shape of lateral facet was concave in 93.9% in the left patella and 100% in the right patella. The shape of lateral facet was flat in 6.1% in the left patella and 0% in the right patella. The mean size of right medial facet was more than left medial facet patella. The shape of medial facet was concave in 2% in the left patella and 10.6% in the right patella. The shape of medial facet was convex in 69.4% in the left patella and 61.7% in the right patella. The shape of medial facet was flat in 28.6% in the left patella and 27.6% in the right patella.

Graphene-mediated stabilization of surface facets on metal substrates

After Chemical Vapor Deposition (CVD), faceted structures are routinely observed on a variety of metal catalyst surfaces in the graphene-covered regions. In spite of having its bare surface flattened through high diffusivity and surface pre-melting at high temperatures, the graphene-covered copper surface still presents faceted structures. Using atomistic simulations, we show the role of graphene in the preservation of the faceted surface morphology at the graphene–copper interface, manifesting as a suppressant against surface melting and surface-specific diffusion. The results of our molecular dynamics simulations are consistent with our experimental observations and demonstrate the thermo-mechanical interfacial surface stabilization role of graphene. Our study provides an understanding applicable to most metal–graphene interfaces and is especially relevant to most metallic catalysts for graphene growth by CVD. Understanding the interaction between graphene and the catalyst surface structure is critical for producing ultra-flat and defect-free graphene.

Special Issue on the 40th Anniversary of University of Macau

Special Issue on the 40th Anniversary of University of Macau

Development of Perovskite Oxide‐Based Electrocatalysts for Oxygen Evolution Reaction (Small 43/2021)

Perovskite Oxide-Based Electrocatalysts In article number 2101605, Shi Chen, Shuangpeng Wang, Guichuan Xing, Hui Pan, and co-workers systematically summarize perovskite oxides as electrocatalysts for efficient oxygen evolution reaction (OER). The catalytic mechanism and descriptors for perovskite oxides are also discussed in detail. Additionally, various strategies to improve the OER catalytic performance of perovskite oxides are carefully reviewed, including composition engineering, crystal facet control, morphology modulation, defect engineering, and hybridization.

Multicomponent TixNbCrAl nitride films deposited by dc and high-power impulse magnetron sputtering

Multicomponent TixNbCrAl nitride films were deposited on Si(100) substrates by reactive direct current magnetron sputtering (dcMS) and high power impulse magnetron sputtering (HiPIMS) in the absence of substrate heating and bias. Three single Ti, Nb, and Cr50Al50 targets were either driven by three dc or three HiPIMS power supplies. The Ti content in the films was varied by tuning the power applied to the Ti target. The composition was determined by ion beam analysis. The nitrogen content is nearly stoichiometric (48–50 at.%) in the HiPIMS series, while the dcMS are understoichiometric (39–45 at.%). The crystal structure, stress and density of the studied film were investigated by X-ray techniques and the microstructure was examined by scanning electron microscopy. All the Ti-containing films for both series exhibit an fcc NaCl-type phase structure. In particular, the dcMS series shows a (111) preferred orientation, resulting in a faceted surface morphology compared to a dense and smooth microstructure of the HiPIMS films. The compressive stress of the HiPIMS series (> 2.0 GPa) is significantly larger than the values of the dcMS series (<0.5 GPa). Nanoindentation measurements show a maximum hardness of 29.9 GPa and Young's modulus of 304 GPa were obtained in the HiPIMS series. The results may promote HiPIMS techniques for the synthesis of complex multicomponent films for the application aspect to protective and hard coatings.

Design of wear facets of mandibular first molar crowns by using patient-specific motion with an intraoral scanner: A clinical study

Statement of problemAlthough computer-aided design has become popular, restorations are typically designed from static occlusion and dynamically by using an average-value virtual articulator. Patient-specific motion recorded by using an intraoral scanner has rarely been used to design restorations, and its design ability has not been analyzed. PurposeThe purpose of this clinical study was to record patient-specific motion by using an intraoral scanner and to analyze its ability to design the morphology of the wear facets on mandibular first molar crowns. Material and methodsAn intraoral scanner was used to scan complete arch digital casts and to record patient-specific motion of 11 participants. Right and left mandibular first molars were selected as the target teeth. The complete crown preparations of the target teeth were virtually prepared on the digital mandibular casts by using the Geomagic Studio 2013 software program. High points were created by elevating the wear facets of the target teeth by 0.3 mm in the occlusal direction to generate digital wax patterns. The Dental System software program was used to design crowns with the anatomic coping design method. Occlusal adjustment with static occlusion (STA crown), with the average-value virtual articulator (DYN crown), and with patient-specific motion (FUN crown) was carried out. The crowns adjusted with these 3 methods were compared with the original wear facets. The mean value and root mean square (RMS) of 3D deviation were measured. One-way ANOVA was used to analyze the influence of the occlusal surface design methods on the morphology of the wear facets (α=.05). ResultsThe STA crowns had the poorest results with the mean ±standard deviation 3D deviation value of 0.15 ±0.05 mm and RMS value of 0.19 ±0.04 mm. The best results occurred in the FUN group, with the mean ±standard deviation 3D deviation value of 0.05 ±0.06 mm and RMS value of 0.13 ±0.03 mm. Significant differences were found among the 3 groups (P<.01). Except for the RMS value between the STA and DYN groups, significant differences were found between groups from the pairwise comparisons. ConclusionsThe occlusal surface of the crowns designed by using the patient-specific motion recorded with the intraoral scanner had the best coincidence with the morphology of the wear facets on the original teeth.

Strong Interfacial Coupling of Tunable Ni-NiO Nanocomposite Thin Films Formed by Self-Decomposition.

The next-generation spintronic devices including memristors, tunneling devices, or stochastic switching exert surging demands on magnetic nanostructures with novel coupling schemes. Taking advantage of a phase decomposition mechanism, a unique Ni-NiO nanocomposite has been demonstrated using a conventional pulsed laser deposition technique. Ni nanodomains are segregated from NiO and exhibit as faceted "emerald-cut" morphologies with tunable dimensions affected by the growth temperature. The sharp interfacial transition between ferromagnetic (002) Ni and antiferromagnetic (002) NiO, as characterized by high-resolution transmission electron microscopy, introduces a strong exchange bias effect and magneto-optical coupling at room temperature. In situ heating-cooling X-ray diffraction (XRD) study confirms an irreversible phase transformation between Ni and NiO under ambient atmosphere. Synthesizing highly functional two-phase nanocomposites with a simple bottom-up self-assembly via such a phase decomposition mechanism presents advantages in terms of epitaxial quality, surface coverage, interfacial coupling, and tunable nanomagnetism, which are valuable for new spintronic device implementation.

Development of Perovskite Oxide-Based Electrocatalysts for Oxygen Evolution Reaction.

Perovskite oxides are studied as electrocatalysts for oxygen evolution reactions (OER) because of their low cost, tunable structure, high stability, and good catalytic activity. However, there are two main challenges for most perovskite oxides to be efficient in OER, namely less active sites and low electrical conductivity, leading to limited catalytic performance. To overcome these intrinsic obstacles, various strategies are developed to enhance their catalytic activities in OER. In this review, the recent developments of these strategies is comprehensively summarized and systematically discussed, including composition engineering, crystal facet control, morphology modulation, defect engineering, and hybridization. Finally, perspectives on the design of perovskite oxide-based electrocatalysts for practical applications in OER are given.