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The microstructure of WC-(Co+Ru) cemented carbides was studied using transmission Kikuchi diffraction (TKD). We report that the Co FCC grains contain Σ3-annealing twins which undergo an incomplete martensitic transformation to form Co HCP laths on cooling below T Ms. The parent Co FCC and product Co HCP phases are related via the Shoji-Nishiyama orientation relationship. Four variants of the Co HCP plates exhibit a special misorientation of 70.5 ± 0.2° 〈 11 2 ¯ 0 〉. A higher transformed fraction was observed in the sample possessing the lower binder content and finer WC grains. We suggest that this is due to the availability of more WC-binder interfaces, which facilitate Co HCP plate nucleation. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The development of high-performance Nd–Dy–Fe–B magnets that minimise the consumption of the scarce rare earth (RE) element Dy remains a major global scientific and technological quest. Here, we designed an alloy microstructure comprising of a uniform Dy-lean core–Dy-rich shell in a series of multi-main-phase (MMP) Nd–Dy–Fe–B magnets. The resulting MMP Dy1 and Dy3 magnets with an overall Dy level of 1 and 3 wt.% possessed values of 0.48 and 0.29 T/wt.% of coercivity increment per unit weight percentage of the Dy addition, respectively. Most importantly, the resulting MMP Dy3 magnet exhibited a high coercivity (2.38 T), an excellent thermal stability of the coercivity (| β | = 0.531%/°C), a high squareness factor (> 95%), all with little diminishment in the remanent magnetisation (1.35 T) and maximum energy product (43.6 MGOe). These properties are superior to the currently available sintered Nd–Dy–Fe–B magnets which utilise higher levels of Dy of 5 wt.%. Via magnetic and multi-scale microstructural characterisation experiments and micromagnetic simulations, the formation of the Dy-lean core–Dy-rich shell microstructure is rationalised via solid-state-diffusion and solution reprecipitation during liquid-phase sintering. The Dy-lean core–Dy-rich shell microstructure and the non-ferromagnetic low-Fe RE-rich grain boundary phase led to the synergistic magnetic performance. This is significant in the context of the MMP Nd–Dy–Fe–B magnets being applied to large-scale production. The present work establishes a pathway for the more sustainable utilisation of Dy in permanent magnets via formation of a uniform core–shell microstructure. [Display omitted] [ABSTRACT FROM AUTHOR]

This observational study on adult Taiwanese cadavers focused mainly on the intersection of buccal branches of the facial nerve with Stensen's duct, using the emergence of Stensen's duct as the reference landmark. Thirty-five cadaveric hemifaces were included in our research. Samples with facial defects due to tumor, trauma, or surgery were all excluded. Buccal branches of the facial nerve were identified according to the Gray's Anatomy 40th edition definition. The distance was measured from the intersection to the emergence of Stensen's duct, running from the anterior border of the parotid gland. In the 35 hemifaces, the number of buccal branch/Stensen's duct intersections ranged from 1 to 5 (average 2.49 ± 1.15). Two-point intersections accounted for 37% (13 hemifaces) of the sample, forming the largest group. Samples of facial nerve buccal branches were divided into four types: Type 1, with two buccal branches, accounted for 37.15% (13/35); Type 2, with three buccal branches, made up 48.59% (17/35) of our samples — the biggest group (Type 2-a was the most frequent pattern among our samples, with two superior buccal branches and one inferior buccal branch, accounting for 34.31% of our samples); Type 3, with four buccal branches, accounted for only 5.7%. Three cases of double Stensen's duct were classified as Type 4, though this is supposed to be a very rare anatomical variation. With Type 2a, the most frequent pattern among our specimens, the distance from the emergence of the Stensen's duct to the emergence point of the first superior buccal branch along the anterior border of the parotid gland was 9.58 ± 5.68 mm. The distance from the emergence point to the emergence of the inferior buccal branch along the anterior border of the parotid gland was 11.03 ± 5.38 mm. The distance (D1) from Stensen's duct to the emergence of the first superiorly located buccal branch of the group Type 2-a was statistically different from the distance (D1) of the other groups (p = 0.02). No direct anastomoses or communicating fibers between upper and lower buccal branches were noted in 11 hemifaces (31%). The distribution of buccal branches was described using the emergence of Stensen's duct as a reference landmark. According to our observations, the relationship between the buccal branches and Stensen's duct was much more complicated than described in previous studies. This was the first study to investigate the complete distribution of buccal branches of the facial nerve emerging from the anterior of the parotid gland, and their relative locations and branching numbers. [ABSTRACT FROM AUTHOR]

Abstract Traditional approaches for increasing the intrinsic coercivity of magnets typically come at the expense of remanence, a dilemma known as intrinsic coercivity-remanence trade-off, leading to a substantial reduction of maximum energy product. New metallurgical processing might offer the possibility of overcoming this trade-off. Here, we achieve a combination of an intrinsic coercivity of 26.9 kOe, a remanence of 11.2 kG, and a maximum energy product up to 26.6 MGOe, which surpasses most of conventional Sm-Co based permanent magnets, by manipulating the gradient of domain wall energy landscape of constituent phases to realize the attractive domain wall pinning in Sm(Co,Fe,Cu,Zr) z permanent magnets. Using powerful atomic-scale analysis technique known as atom probe tomography and micromagnetic simulations, we reveal that an enlarged attractive domain wall pinning strength results in the substantial coercivity enhancement with little sacrifice of remanence and maximum energy product in the Cu-particle-alloyed magnet. These results provide atomic-level insights into the coercivity mechanism of rare earth permanent magnets, with the methodology offering exciting possibilities for quantitative analyses and prediction between compositions and magnetic properties of other magnetic materials. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Quantification of microstructure, especially grain size, in polycrystalline materials is a vital aspect to understand the structure-property relationships in these materials. In this paper, representative characterization techniques for determining the grain size, including optical microscopy (OM), electron backscatter diffraction (EBSD) in the scanning electron microscopy (SEM), and atomic force microscopy/magnetic force microscopy (AFM/MFM), are thoroughly evaluated in comparison, illustrated by rare-earth sintered Nd-Fe-B permanent magnets. Potential applications and additional information achieved by using aforementioned characterization techniques have been discussed and summarized. [ABSTRACT FROM AUTHOR]

Zinc ion capacitors (ZICs) are promising energy storage systems inheriting the characteristics of zinc ion batteries and supercapacitors. The development of high-performance, green and low-cost method for preparing carbon materials is essential for the development of ZICs. In this work, we report the fabrication of porous carbon from physical and chemical dual cross-linked lignin in a one-step pyrolysis process. The obtained porous carbon ZnLFK-PC demonstrates the highest specific capacitance of 333.0 F g−1 at 0.2 A g−1 with a capacitance retention of 59 % (from 0.2 to 20 A g−1). When used as the carbon cathode for ZIC, it shows the highest capacity of 123.7 mA h g−1 with an energy density of 97.8 Wh kg−1 at 0.5 A g−1. The electrochemical performance is superior to many other biomass-derived porous carbon cathodes. Moreover, the underlying mechanism is evaluated via impedance analysis. The utilization of lignin is of great importance for sustainable development, and this work presents an alternative practice of using lignin resource for high-performance ZICs. [Display omitted] • Composition-structure optimized porous carbon was prepared from bio-resource lignin via one-step pyrolysis. • The ZnLFK-PC carbon electrode exhibited the highest specific capacitance of 333.0 F g−1 at 0.2 A g−1. • The ZnLFK-PC cathode delivered a high capacity of 123.7 mA h g−1 and an energy density of 97.8 Wh kg−1 at 0.5 A g−1. • Electrochemical impedance tests were used to probe energy storage mechanism on lignin derived cathodes in capacitors. [ABSTRACT FROM AUTHOR]

Fluctuations in energy distribution during additive manufacturing (AM) can result in spatial and temporal thermal transients. These transients can lead to complexities, most significantly when alloys with multi phases are subjected to AM. Here we unveil such complexities in a duplex stainless steel, where we report an unanticipated formation of a Ni-Mn-Si rich phase at grain boundaries and a local fluctuation in Cr and Fe concentrations in regions close to grain boundaries, providing Cr-rich precursors for Cr 2 N formation after laser powder bed fusion (LPBF). The formation of these phases is believed to be due to severe thermal gyrations and thermal stresses associated with LPBF resulting in a high-volume fraction of ferrite supersaturated with N and Ni, and a high density of dislocations accelerating diffusion and phase transformations. [Display omitted] [ABSTRACT FROM AUTHOR]

The influence of solute drag effects on austenite grain growth in microalloyed steels has been overshadowed by the well-established phenomenon of Zener pinning associated with a dispersion of fine precipitates. Enhanced toughness in the weld heat-affected zone (HAZ) of high Nb steels suggests that microalloying effects are still operative at peak temperatures even beyond known precipitate stability. As the cornerstone for unveiling the solute drag effect, the solute concentration in the matrix should be accurately measured. In this work, we compared inductively coupled plasma mass spectroscopy (ICP-MS) and atom probe tomography (APT) in determining the extent of Nb dissolution as a function of increasing temperature in two commercial American Petroleum Institute steel grades with different levels of Nb and marked variations in weld HAZ toughness. Both techniques demonstrated that the majority of Nb exists in solid solution at the peak temperatures. APT provided a more consistent determination of soluble Nb, in a better agreement with thermodynamic calculations, whilst ICP-MS underestimated the concentration of Nb in the matrix. This work provides valuable insights in determining soluble Nb concentration in steels. [Display omitted] • Nb content in solid solution was analysed as a function of temperature using ICP-MS and APT techniques. • Experimental results were compared with thermodynamic simulations. • High Nb steel provides increased levels of soluble Nb following thermal cycles. • APT provided a more consistently reliable determination of soluble Nb. • ICP-MS qualitatively recorded Nb dissolution as a function of temperature but in general recorded lower values due to limitations in sample preparation. [ABSTRACT FROM AUTHOR]

The design of additively manufactured metallic alloys with tailored mechanical properties requires a detailed understanding of the microstructural evolution throughout the printing process. In Ti-6Al-4V, this involves a complex combination of phase transformations, leading to microstructural and property variations within a single as-fabricated build. The origin of such property variations and the sequence of phase changes occurring during the cyclic heating and cooling process remain uncertain. We have studied the phase transformation pathway by following how, in particular, the β phase growth varies within the build. Samples manufactured by electron beam powder bed fusion were analysed using electron microscopy and atom probe tomography techniques. We demonstrate that a significant β phase fraction variation occurs within a given build plane. We reveal that the high-temperature β phase can be separated into two categories, depending on whether it was retained from cooling from above the β transus temperature, or nucleated below it. This is the first direct evidence of the coexistence of both types of β transformation products in Ti-6Al-4V. The abrupt cyclic nature of the additive manufacturing process is what has facilitated this unusual transformation sequence. The work provides a complete and general description of the phase transformation pathway, informed by these observations. The implication of the phase transformation pathway on hardness is discussed in relation to chemical variation and oxygen pickup. [Display omitted] [ABSTRACT FROM AUTHOR]

As-sintered multi-main-phase Nd-Ce-Fe-B permanent magnets typically exhibit a higher coercivity than as-sintered single-main-phase Nd-Ce-Fe-B magnets with identical content of Ce. To clarify the microstructural features that are relevant to the coercivity, as-sintered multi-main-phase Nd-Ce-Fe-B permanent magnets are characterised by high-resolution magnetic force microscopy and atom probe tomography down to the atomic scale. Though inhomogeneous distribution of rare earth elements (Nd, Pr, and Ce) is observed inside 2:14:1 matrix grains, Ce atoms unexpectedly show similar partitioning behaviour (∼14–27% of rare earth element) at the edge of these grains in the vicinity of rare earth-rich grain boundary compared with as-sintered single-main-phase Nd-Ce-Fe-B magnets with a 20% Ce substitute of Nd and Pr. By contrast, the observation of stripe-liked magnetic domains pinned at the grain boundaries and a thin (Nd,Pr,Ce)-rich grain boundary with a composition of Nd 9.9 Pr 2.6 Ce 19.0 Fe 65.3 Co 1.9 Balance 1.3 (at.%) jointly indicates the enrichment of Ce in grain boundaries benefit to the magnetic isolation of neighbouring matrix grains in the as-sintered state. Unusual Ce-rich clustering regions are also observed in the grain boundary, which also contribute to the coercivity enhancement. The segregation of Ce, Co, and Cu and rare-earth-Cu clusters are only observed at the interface between rare earth-Cu rich phase and matrix phase while no obvious elemental segregation and clusters are observed at the interface between the rare earth-Ga rich phase and matrix phase, suggesting the occurrence of rare earth-Cu rich phase may be one of the reasons for achieving high coercivity. These findings offer fresh insights into the as-sintered multi-main-phase Nd-Ce-Fe-B permanent magnets. Image 1 • High intrinsic coercivity is achieved in the as-sintered multi-main-phase Nd-Ce-Fe-B magnets. • The formation of thin (Nd,Pr,Ce)-rich grain boundary in the as-sintered state. • The formation of Ce-rich clustering regions at grain boundaries in the as-sintered state. • The segregation of Cu at the interfaces between the rare earth-Cu rich phase and matrix phases. • No Ga segregation at the interfaces between the rare earth-Ga rich phase and matrix phases. [ABSTRACT FROM AUTHOR]

• Intragranular rare earth (RE)-rich phase was characterized in strip-cast Nd-Fe-B flakes. • The intragranular RE-rich phase is made up of amorphous and crystalline regions. • Cu, Co, and Ga are enriched in the amorphous region. • The crystalline region is made up of hexagonal LRE-rich and cubic LRE/HRE/O-rich phases. • The formation of these intragranular glass/crystal phases was proposed. Intragranular rare earth-rich phases play a vital role in affecting the intrinsic coercivity of sintered Nd-Fe-B permanent magnets. To explore the origin of these intragranular rare-earth-rich phases, the starting material-strip cast Nd-Fe-B flakes were characterized by a variety of high-end microscopy techniques. It was surprisingly found that the intragranular rare-earth-rich phase is spherical in a diameter of ~150–300 nm and consists of amorphous regions rich in additive elements (e.g., Cu, Co, and Ga) and crystalline regions which are a combination of hexagonal light-rare-earth-rich phases and body centered cubic phases rich in light and heavy rare earth, and oxygen. Amorphous interfacial layers between the glass/crystal particles and the crystalline matrix were observed, probably due to insufficient time to reach a crystalline equilibrium state. Based on the microstructural observation, we proposed a formation mechanism of these intragranular glass/crystal conjugated particles in strip cast Nd-Fe-B flakes, which may facilitate to minimize the volume of these detrimental intragranular phases during the strip casting process. [ABSTRACT FROM AUTHOR]

[Display omitted] • 2205 DSS shows similar pitting potentials and passive current densities at RT irrespective of processing route. • Cr is depleted adjacent to intergranular Cr 2 N particles but remains above the critical value for passivation. • As-built LPBF 2205 DSS shows a lower CPT compared to its hot-rolled counterpart. • Post-AM heat treatment enhances the critical pitting temperature to the level of the hot-rolled DSS. The effects of additive manufacturing (AM) and post-AM heat treatment on microstructural characteristics and pitting corrosion of 2205 duplex stainless steel were studied and benchmarked against its conventionally hot-rolled counterpart. The rapid solidification and possible loss of N associated with AM resulted in a non-equilibrium microstructure dominated by δ-ferrite with a minor fraction of austenite and abundant Cr 2 N precipitation. Atom probe tomography revealed that no depletion of Cr occurs around intragranular Cr 2 N. A deduction in Cr was observed adjacent to intergranular Cr 2 N particles, however, Cr content in these regions remained above the critical value of 13 wt%. Post-AM heat treatment was effective in restoring the duplex microstructure while dissolving the Cr 2 N precipitates. Although the pitting resistance in the as-built AM specimen was lower than that of its hot-rolled counterpart, it was fully recovered after post-AM heat treatment. [ABSTRACT FROM AUTHOR]

Understanding the pathways and mechanisms of human tooth decay is central to the development of both prophylaxes and treatments, but only limited information is presently available about the initiation of caries at the nanoscale. By combining atom probe tomography and high-resolution electron microscopy, we have found three distinct initial sites for human dental enamel dissolution: a) along the central dark line (CDL) within carbonated apatite nanocrystals, b) at organic-rich precipitates and c) along high-angle grain boundaries. 3D maps of the atoms within hydroxyapatite nanocrystallites in sound and naturally-decayed human dental enamel reveal a higher concentration of Mg and Na in the CDL. The CDL is therefore thought to provide a pathway for the exchange of ions during demineralization and remineralization. Mg and Na enrichment of the CDL also suggests that it is associated with the ribbon-like organic-rich precursor in amelogenesis. Organic-rich precipitates and high-angle grain boundaries were also shown to be more vulnerable to corrosion while low-angle grain boundaries remained intact. This is attributed to the lower crystallinity in these regions. [ABSTRACT FROM AUTHOR]

Highlights • Surface analysis of nano-textured structure in the vertical LED is characterized using non-destructive techniques (NDT). • NDT provide non-contact, local, robust, sophisticated and non-destructive material characterization methodology adequate for measuring surface roughness and stress-states. • Surface topography of nano-textured surface of the LED has roughness of ∼300 nm and in a compression stress-state of 0.667 GPa with emission peak wavelength of 442 nm. • Texture engineering does not affect the active region of the LED. • Prospective optimizations are suggested in surface engineering for light enhancement in LEDs. Abstract In this work, the nano-textured surface of a GaN-based vertical light emitting diode (VLED) is characterized using a unified framework of non-destructive techniques (NDT) incorporating scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy, Photoluminescence (PL), and X-ray diffraction (XRD) to optimize the light output efficiency. The surface roughness of ∼300 nm is revealed by AFM. Compressive stress-state of 0.667 GPa in the GaN surface is indicated by the E 2 (high) and A 1 (LO) phonon peak values at 569 cm−1 and 736 cm−1, respectively, in Raman spectrum and the wavelength at 442 nm rather 450 nm in PL spectrum. Without damaging the LED, surface analysis by NDT helps to advance the understanding of the optimized angular light redistribution subject to the high-roughness surface and the negative impacts of the stress induced at the top GaN layer, which leads to the optical efficiency degradation of the VLED. Furthermore, the impact of texturing on underneath n-GaN and MQWs layers is investigated via SEM-based transmission Kikuchi diffraction (TKD) and aberration-corrected scanning transmission electron microscopy (AC-STEM) and revealed a smooth surface morphology and good crystalline quality, indicating that the etch-induced damage by texture engineering does not impair the active region of the VLED. Accordingly, prospective optimizations are suggested in the context of surface engineering for light enhancement in VLEDs. [ABSTRACT FROM AUTHOR]

Pursing high coercivity‒remanence synergy is a common challenge for permanent magnets, particularly for the La/Ce-based RE‒Fe‒B (RE: rare earth) magnets that usually exhibit drastic magnetic dilution. Here we apply the Pr 80 Ga 20 grain boundary diffusion process (GBDP) to overcome the coercivity‒remanence trade-off of the LaCe-40 (La‒Ce/total RE = 40%) magnet and yield the record-high magnetic performance with H cj = 16.1 kOe, B r = 13.1 kG and (BH) max = 41.4 MGOe upon high La‒Ce substitution. One of the prominent merits of the PrGa GBDP is to assist the formation of anti-ferromagnetic RE 6 Fe 13 Ga phase at triple junctions and grain boundaries (GBs), which is observed for the first time within the RE‒Fe‒B diffusion system. The synergetic effects of Pr to enlarge the volume fraction of RE-rich phase and Ga to optimize its wettability also facilitate the formation of continuous non-ferromagnetic RE-rich phase at GBs, being another prominent merit of the PrGa GBDP. The anti-ferromagnetic RE 6 Fe 13 Ga and non-ferromagnetic RE-rich GBs to decouple neighboring ferromagnetic matrix grains, and the Pr-rich shell to strengthen local magnetocrystalline anisotropy jointly enhance the coercivity, as demonstrated by the microstructural characterization and micromagnetic simulation. The first order reversal curve and Kerr microscopy further reveal the impedance of the nucleation of reversal domains in the PrGa GBDP LaCe-40 magnet, transforming from multi-domain reversal to single-domain reversal. Moreover, Pr infiltration into the matrix grains increases the local magnetization and leads to raised remanence by 0.2 kG. The above work provides a clear picture of the synergetic effects between Pr and Ga towards fully exploiting paragenetic La‒Ce alloy and developing the low-cost commercial-grade permanent magnets. [Display omitted] [ABSTRACT FROM AUTHOR]

The dry sliding wear behaviors of the face-centred cubic (f.c.c.) high entropy alloys carbon-doped Fe 40.4 Ni 11.3 Mn 34.8 Al 7.5 Cr 6 and equiatomic CoCrFeMnNi were determined under ambient conditions and compared with that of 316 stainless steel at two sliding velocities and in argon at a slow sliding velocity. Scanning electron microscopy, energy dispersive X-ray spectrometry, electron backscattered diffraction, X-ray photoelectron spectroscopy, and atom probe tomography analyses were employed to characterize the worn microstructures. It was found that in air at the slow sliding velocity of 0.1 m/s C-doped FeNiMnAlCr exhibited a much lower wear rate of 3.0 × 10−5 mm3/N/m compared to either 316 stainless steel (2.9 × 10−4 mm3/N/m) or CoCrFeMnNi (3.4 × 10−4 mm3/N/m). In contrast, both in argon at this slow sliding velocity and in air at the high sliding velocity of 1.0 m/s, all three material showed similar wear rates of ~ (2.4 ± 0.6) × 10−5 mm3/N/m and ~ (1.2 ± 0.3) × 10−5 mm3/N/m, respectively, indicating the strong effect of the environment and pin tip temperature on the wear rates. The oxide that formed on the C-doped FeNiMnAlCr alloy was found to be more stable and durable than that on either the CoCrFeMnNi or on the 316 stainless steel, and the wear debris from C-doped FeNiMnAlCr had the smallest diameter (3 μm) and the lowest oxygen content of 39 at. %. Greater Al 2 O 3 and less Fe 2 O 3 , MnO x or Cr 2 O 3 on the worn surface of C-doped FeNiMnAlCr contributed to a peeled-off or delaminated morphology with a higher oxygen content of 46 at. % compared to the worn surfaces of the 316 stainless steel and the CoCrFeMnNi, which both exhibited grooved worn surfaces with lateral cracks and lower oxygen contents of 7.5 at. % and 31 at. %, respectively. The harder Al 2 O 3 oxide film was stable and adherent during wear testing and helped protect the worn pin's tip, which was the reason for the increased wear resistance of the C-doped FeNiMnAlCr. The wear protection mechanism of 316 stainless steel was attributed to a hard mechanically deformed layer, while the CoCrFeMnNi lacked protection from either the oxide film or a hard deformed layer. Unlabelled Image • C-doped FeNiMnAlCr HEA has a lower wear rate than 316 stainless steel and CoCrFeMnNi HEA in air. • The worn surface of C-doped FeNiMnAlCr HEA was the flattest with the highest oxygen content. • XPS indicated that the C-doped FeNiMnAlCr HEA worn surface contained a large amount of Al 2 O 3. • The oxides formed on the C-doped FeNiMnAlCr HEA pin were more stable and adherent. • The wear mechanism of the C-doped FeNiMnAlCr HEA is predominantly oxidative wear. [ABSTRACT FROM AUTHOR]