Low-index Planes Research Articles

Microgalvanic cell-mediated green synthesis of Cu2O nanocubes with (100) facets for boosting dopamine hydrochloride sensing performance

Despite numerous efforts have been made on exploring the preparation, properties and application of Cu2O nanocrystal, there is still a lack of a facile and green synthesis strategy to obtain well-defined Cu2O nanocubes (NCs). And exploration of the superior low-index lattice plane of Cu2O in electrochemical sensing is also inadequate. Herein, we proposed a Ni(OH)2-mediated in-situ synthetic strategy for the preparation of Cu2O NCs enclosed by low-index facets with simple procedure, mild temperature and low energy-consumption. The Ni(OH)2 sites not only facilitated the contact between Cu2+ and the substrate Ni foam (NF), but also can combine with the NF to act as a primary battery to regulate the nucleation and growth rate of Cu2O (100) facets. Benefiting from the high ratio of exposed electroneutral (100) lattice planes of nanocubes, the Cu2O NCs formed on Ni(OH)2-abundant Ni Foam (Cu2O NCs/NFEO) exhibited a wide linear range (3.25–1178.8 μM), a low detection limit (1.86 μM) and a high sensitivity (900 μA mM−1 cm−2) in dopamine hydrochloride (DAH) electrochemical sensing. This work expects to provide more clues about the relationship between different dominant low-index facets of Cu2O NCs and electrochemical sensing performance towards DAH, and thereby contributes to the development of functional materials based on Cu2O nanocrystals with desirable facets.

Atomic-scale bonding strength and failure mechanisms of HfC/Ni/Ni3Al interfaces on low-index crystal planes: A combined HRTEM and first-principles study

The carbide/matrix interface in superalloys is susceptible to cracking under mechanical stress, yet the failure mechanisms require further investigation. The cohesive strength and stability of 32 interface models, including HfC(001)/Ni(001), HfC(011)/Ni(001), HfC(111)/Ni(001), HfC(001)/Ni3Al(011), and HfC(111)/Ni3Al(111) within the DZ125 superalloys, were investigated using first-principles calculations and experimental methods. The results indicate that the majority of interfaces demonstrate negative adhesion work (Wad), indicating instability. However, Bridge4 model in HfC(001)/Ni3Al(011) show higher Wad and lower interface energy, suggesting improved stability. The interfacial cohesion is attributable to strong Ni-C covalent bonds. But interfacial fracture toughness results reveal that the majority of models are more susceptible to fracture at the interface. Fracture morphology analysis from tensile tests at room temperature and endurance tests at 760 °C/725 MPa confirms that cracks primarily initiate at the carbide/matrix interface. This study suggests that introducing Ta atoms could improve interface strength, as Ta-rich carbides reduce interfacial energy while increasing elastic energy, resulting in the formation of skeletal structures. The relationship between Hf-rich and Ta-rich carbides and their respective morphology was investigated. The findings provide insights into the failure mechanisms of carbide/matrix interface and offer theoretical guidance for enhancing interface strength in superalloy applications.

Ostwald-Ripening Induced Interfacial Protection Layer Boosts 1,000,000-Cycled Hydronium-Ion Battery.

Collapsing and degradation of active materials caused by the electrode/electrolyte interface instability in aqueous batteries are one of the main obstacles that mitigate the capacity. Herein by reversing the notorious side reactions include the loss and dissolution of electrode materials: as we applied Ostwald ripening (OR) in the electrochemical cycling of a copper hexacyanoferrate electrode in a hydronium-ion batteries, the dissolved Cu and Fe ions undergo a crystallization process that creates a stable interface layer of cross-linked cubes on the electrode surface. The layer exposed the low-index crystal planes (100) and (110) through OR-induced electrode particle growth, supplemented by vacancy-ordered (100) superlattices that facilitated ion migration. Our design stabilized the electrode-electrolyte interface considerably, achieving a cycle life of one million cycles with capacity retention of 91.6%, and a capacity retention of 91.7% after 3000 cycles for a full battery.

Optimized EBSD-TEM method for the investigation of Al/Al2O3 interfacial orientation mismatch

The combined electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) method has been commonly applied to investigate material interfaces, from the perspectives of orientation and atomic structure. However, the loose combination is inadequate to capture some slight deviation from the ideal mismatch of interface, which limits an in-depth understanding of the interface. In this study, the combined EBSD-TEM method was systematically optimized and applied to investigate Al-Al2O3 heterogeneous nucleation interface. In this optimized EBSD-TEM method, the cylindrical equidistant projection was employed to illustrate the orientation mismatch relationship instead of the widely used pole figure. Lattice planes and directions from two phases are systematically presented in one figure, which provides a thorough perspective to identify all the potential matching features within the interface, meanwhile ensures a precise guidance for TEM sampling and observation. Such guidance is crucial for interface investigations, thereby this optimized EBSD-TEM method has great potential to be widely applied. Complex interface configurations of Al-Al2O3 interfaces were revealed, including the tilting of Al phase low-indexed planes relative to the interface and the deviations of matched lattice direction pairs between two phases. The complex interface configurations urge further development in the theory of nucleation interface mismatch.

N2 as an Efficient IR Probe Molecule for the Investigation of Ceria-Containing Materials.

Ceria and ceria-based catalysts are very important in redox and acid-base catalysis. Nanoceria have also been found to be important in biomedical applications. To design efficient materials, it is necessary to thoroughly understand the surface chemistry of ceria, and one of the techniques that provides such information about the surface is the vibrational spectroscopy of probe molecules. Although the most commonly used probe is CO, it has some disadvantages when applied to ceria and ceria-based catalysts. CO can easily reduce the material, forming carbonate-like species, and can be disproportionate, thus modifying the surface. Here, we offer a pioneering study of the adsorption of 15N2 at 100 K, demonstrating that dinitrogen can be more advantageous than CO when studying ceria-based materials. As an inert gas, N2 is not able to oxidize or reduce cerium cations and does not form any surface anionic species able to modify the surface. It is infrared and transparent, and thus there is no need to subtract the gas phase spectrum, something that often increases the noise level. Being a weaker base than CO, N2 has a negligible induction effect. By using stoichiometric nano-shaped ceria samples, we concluded that 15N2 can distinguish between surface Ce4+ sites on different, low index planes; with cations on the {110} facets and on some of the edges, Ce4+-15N2 species with IR bands at 2258-2257 cm-1 are formed. Bridging species, where one of the N atoms from the molecule interacts with two Ce4+ cations, are formed on the {100} facets (2253-2252 cm-1), while the interaction with the {111} facets is very weak and does not lead to the formation of measurable amounts of complexes. All species are formed by electrostatic interaction and disappear during evacuation at 100 K. In addition, N2 provides more accurate information than CO on the acidity of the different OH groups because it does not change the binding mode of the hydroxyls.

A home-made nanoporous gold microsensor for lead(II) detection in seawater with high sensitivity and anti-interference properties.

A nanoporous gold microelectrode (NPG-μE) was fabricated and used for Pb(II) detection in seawater samples via square wave anodic stripping voltammetry (SWASV). The Au microelectrode (Au-μE) was fabricated by embedding a gold microfiber into a Pasteur pipette, and its surface was further modified by an anodization-electrochemical reduction (A-ECR) method, yielding the NPG-μE. The fabricated electrodes were characterized by cyclic voltammetry (CV) and field emission scanning electron microscopy (FE-SEM) for electrochemical and structural morphological investigations. SWASV results show a Pb(II) stripping peak at around -0.05 V vs. Ag/AgCl, sat. KCl, which is unusual for common Pb(II) detection (typically occurring at around -0.40 V) in anodic stripping voltammetry (ASV) analysis. The Pb(II) detection at less negative stripping potential is more beneficial. Hence, it exhibited anti-interference properties with Cd(II), which is attributed to the preferential deposition and stripping of the target analyte on the low-indexed crystal planes of the NPG structure. The calibration plot obtained by SWASV was linear in the concentration range of 0.1-10 μM, and the detection limit was found to be 57 nM (correlation coefficient of 0.9974). The NPG microsensor presented a 15-fold enhanced current response compared to Au-μE, with excellent sensitivity (27.2 μA μM-1 cm-2). The application of the NPG microsensor was examined by detecting Pb(II) in seawater samples, and a satisfactory performance was obtained.

Fracture of the C15 CaAl2 Laves phase at small length scales

The cubic C15 CaAl2 Laves phase is an important brittle intermetallic precipitate in ternary Mg–Al–Ca structural alloys. Although knowledge of the mechanical properties of the co-existing phases is essential for the design of improved alloys, the fracture toughness of the C15 CaAl2 intermetallic has not yet been studied experimentally due to limitations posed by macroscale testing of defect-free specimens. Here, miniaturised testing techniques like micropillar splitting and microcantilever bending methods are used to experimentally determine the fracture toughness of the CaAl2 Laves phase. It is found that the toughness value of ~ 1 MPa·√m obtained from pillar splitting with a sharp cube corner geometry is largely insensitive to sample heat treatment, the ion beam used during fabrication, micropillar diameter, and surface orientation. From correlative nanoindentation and electron channelling contrast imaging supported by electron backscatter diffraction, fracture is observed to take place mostly on {011} planes. Atomistic fracture simulations on a model C15 NbCr2 Laves phase showed that the preference of {011} cleavage planes over the more energetically favourable {111} planes is due to lattice trapping and kinetics controlling fracture planes in complex crystal structures, which may provide insights into the experimental results for CaAl2. Using rectangular microcantilever bending tests where the notch plane was misoriented to the closest possible {112} cleavage plane by ~ 8° and the closest {001}, {011}, and {111} planes by > 20°, a toughness of ~ 2 MPa·√m was determined along with the electron microscopy observation of significant deviations of the crack path, demonstrating that preferential crystallographic cleavage planes determine the toughness in this material. Further investigation using pentagonal microcantilevers with precise alignment of the notch with the cleavage planes revealed similar fracture toughness values for different low-index planes. The results presented here are the first detailed experimental study of fracture toughness of the C15 CaAl2 Laves phase and can be understood in terms of crack plane and crack front-dependent fracture toughness.Graphical

Effect of Si doping on elastic-plastic fracture toughness (JIC) of T91 ferritic/martensitic steel in liquid lead-bismuth eutectic

This work was devoted to understanding the effect of Si doping (1.27 wt%) on elastic-plastic fracture toughness (JIC) of T91 ferritic/martensitic (F/M) steel in liquid lead-bismuth eutectic (LBE, Pb44.5Bi55.5, wt%) under various parameters. The results showed that Si doping significantly promoted occurrence of liquid metal embrittlement (LME) and led to more severe degradation of fracture toughness at 350 °C, especially in oxygen-poor LBE. The LME susceptibility of T91-Si steel was found to be nearly independent on the loading speeds, while T91 F/M steel exhibited a stronger LME effect when the loading speed was decreased from 0.02 mm/min to 0.002 mm/min. Oxygen concentration had a mild effect. Detailed microstructural analyses showed that the fracture behavior of the T91-Si steel in LBE environment at 350 °C was analogous to cleavage fracture and the crack propagation was mainly transgranular. The crack wall was quite rough and locally faceted to low-index crystallographic planes of {110}. Numerous dislocations were also present in the vicinity of the crack tip. No solid evidence of diffusion of Pb and Bi into the steel bulk was discovered even at the atomic scale, which strongly suggests a crack tip surface adsorption-based LME mechanism.

Low traces of acetone detection with WO3-based chemical sensors

This work presents the ability of WO3-based sensors to detect low traces of acetone, specifically within the range of 0.25–5 ppm, specific to the in-field atmosphere. The WO3 powder was synthesised through the hydrothermal method. Morpho-structural investigations showed a monoclinic structure and a good crystallization of the WO3 powder, containing well-grown and faceted grains along low-index crystallographic planes. The paste obtained by mixing the powder with propanediol was screen-printed as a thick layer onto commercial alumina substrates, obtaining the chemical sensors. A dynamic computer-controlled Gas Mixing System was utilized to ensure controlled airflow with variable relative humidity and acetone concentrations. The sensor response was explained based on physico-chemical equations, taking into consideration pre-adsorbed species of oxygen and water, both of which are relevant constituents of atmospheric conditions. The results highlight the applicative potential of WO3, having a good signal-to-noise ratio in relative humidity conditions up to 90% and a pronounced sensitive selectivity to acetone.

Nanoisland Formation on the Low Index Planes of Pt By Repeated Electro-Oxidation and-Reduction

Pt-based electro-catalysts are the most common cathode material in proton exchange membrane fuel cells given their high oxygen reduction reaction activity and stability. However, practical applications are limited by catalyst performance loss and degeneration. A main cause for this is nanoscale Pt surface restructuring, which occurs upon formation and reduction of a Pt surface oxide. During oxidation, a fraction of the Pt surface atoms are extracted in a process known as “place-exchange” from the electrode and are bound at specific sites in an oxide about 1 – 4 Å above the surface [1]. Upon subsequent oxide reduction, these atoms as well as the vacancies from which they originate can agglomerate, leading to the nucleation of adatom and vacancy islands. If this process is repeated, nanoislands with a well-defined lateral size of about 20 – 60 Å are grown [2-6]. Detailed studies of this growth process have been performed on the Pt(111) electrode [2-6], revealing two distinct growth regions which are characterized by different vertical scaling exponents [3].For the development of catalysts with superior long-term stability, a more detailed knowledge of the restructuring of the other low index planes of Pt is required. In our recent study of the Pt oxides on Pt(111) and Pt(100) we already showed a strong dependence of the structural stability of the surface on differences in the atomic-scale oxide structure formed on those two surface orientations [1]. However, the influence of surface structure on the nanoisland growth after repeated oxidation and reduction is largely unclear.We present a comparative operando grazing incidence small angle X-ray scattering (GISAXS) study of the nanoisland formation on Pt(111), Pt(100) and Pt(110) in acidic electrolyte. The GISAXS measurements of the nanoisland growth were performed at a high photon energy of >70 keV, which lowered background scattering from the electrolyte, enabling us to resolve the islands after the very first ox./red. cycle. Differences in island shape and growth behaviour on the low index planes will be discussed.We gratefully acknowledge financial support by the Deutsche Forschungsgemeinschaft via project no. 418603497, MA 1618/23-1 and the BMBF via 05K19FK3.References Fuchs et al., Nat. Catal. 3, 754–761 (2020)Sugawara and K. Itaya, J. Chem. Soc., Faraday Trans. 185, 1351-1356 (1989)Jacobse et al., Nat. Mater. 17 (3), 277-282 (2018)J. Rost, et al., Nat. Commun. 10, 5233 (2019)Ruge et al., J. Am. Chem. Soc. 139, 4532 (2017)Jacobse, et al. ACS Cent. Sci. 5 (12), 1920–1928 (2019)

Epitaxial relationship of NiO on (02) β-Ga2O3

We investigated the epitaxial relationship of an electron-beam-evaporated NiO film on a custom-ordered (02) β-Ga2O3 substrate with a surface orientation rotated by 13.8° around [010] axis relative to the commonly-used (001) substrate. X-Ray diffraction and transmission electron microscopy measurements confirmed that the film was monocrystalline with out-of-plane and in-plane alignments of (110)NiO||(02)β-Ga2O3 and NiO||[010]β-Ga2O3, respectively, indicating that the film grew on the substrate while maintaining the orientation of the cubic-close-packed (ccp) oxygen sublattice across the interface. The use of the low-index (110) epitaxial plane within the ccp lattice may be preferred for pn-heterojunctions over the higher-index (331) plane on the (001) β-Ga2O3 substrate.

Dislocation-mediated migration of the α/β interfaces in titanium

Interphase boundaries are essential in the deformation and phase transformations in titanium (Ti) alloys. While static structures of semicoherent α/β interfaces in various Ti alloys have been carefully examined, their migration behavior at atomic scales is far less clear. In this study, we employed molecular dynamics simulations to investigate the migration of the semicoherent α/β interface in pure Ti. The interface migration behavior shows a shear-coupled feature with the interface dislocation glide and a macroscopic shear. The simulation reveals that both the glide direction of the dislocations with respect to the interface and the dislocation spacing strongly influence the migration rate, and the low-index glide plane of the interface dislocation plays a minor role. The dependence of interface mobility on temperatures confirms the critical role of thermal activation during the interface migration, especially for activating the interface dislocation glide. Furthermore, the shear-coupled interface migration driven by element partition is simulated using a newly developed Ti-Mo potential, consistent with the displacive-diffusional features previously observed in the surface precipitates. The simulated interface migration mode is validated by comparing it with the crystallography features of surface precipitates in a Ti-Cr alloy. The interface energy and mobility obtained from simulations further explain why the distinctive crystallographic features of the surface precipitates observed experimentally are favored over other candidate interfaces. The present study has explored an approach for systematically examining thermodynamic and kinetic factors governing the development of phase transformation crystallography at different temperatures and chemical driving forces.

Multiscale microstructural consideration of enhanced shear strength in TiAl intermetallic/K4169 alloy composite joints prepared by vacuum brazing with (Ti, Zr)-Ni-based amorphous filler metal

TiAl intermetallic could be used to replace Ni-based alloy in assemblies to generate excellent specific strength. A (Ti,Zr)-Ni-based amorphous filler metal Ti21.25Zr25Ni25Cu18.75 (at.%) was designed using a cluster-plus-glue-atom model to successfully vacuum braze K4169 and TiAl bimetallic assemblies. At various brazing temperatures and holding time, the quantitative relationships between lattice distortion, grain boundary, dislocation density, and hardness, elastic modulus, shear strength of the joints were investigated. Meanwhile, the fracture mechanism of the joints was revealed. The brazed seam mainly consisted of solid diffusion reaction layers (Zones I and III) and filler metal residue zone (Zone II). When the brazing temperature increased to 1030 °C, grain refinement occurred in the brazed seam. Zone I was primarily composed of (Ni)ss[0-11]+TiNi[011]/(Cr,Fe,Ni)ss[0-11]/(Ti,Zr)Ni[0-1-1]+(Cr,Fe,Ni)ss[0-11]. The (Ti,Zr)(Ni,Cu)[001] and (Ti,Zr)(Ni,Cu)[101] intermetallic compound-based solid solutions were formed in Zone II. And the lattice distortion of (Ti,Zr)(Ni,Cu)[101] and (Ti,Zr)(Ni,Cu)[001] was 32.05% and 14.82%, respectively. As a result, the proportion of low angle grain boundaries (LAGBs) and deformed grains in Zone II rose to 38.6% and 38.7%. In Zones I and III, the proportion of LAGBs reduced to 8% and 3.4%, respectively. As the holding time increased, the long-range diffusion of Al in Zone II caused the (Ti,Zr)(Ni,Cu)[001] with cubic structure to transform into (Ti,Zr)(Ni,Cu,Al)[00-1] with hexagonal crystal system structure, where the lattice distortion was 4.42% and 10.49% for a and c. At 1030 °C/10 min, the average geometrically necessary dislocation densities (GNDs) in Zones I, II and III were 9.87 × 1014 m−2, 8.55 × 1014 m−2 and 11.4 × 1014 m−2, respectively. Therefore, the shear strength of joints reached 322 MPa due to the lattice distortion, dislocation strengthening and fine grain strengthening. Meanwhile, the plastic and brittle hard phases were generated in Zone II and displayed a mechanical interlocking structure that contributed to the performance of the joint. Both (Ti,Zr)(Ni,Cu)[001] and (Ti,Zr)(Ni,Cu)[101] in Zone II formed along different low-index cleavage planes during transgranular fracture. The cracks initiated in this region extended to the interface between Zones I and II and exhibited bimodal grain characteristics.

A combined simulation and experimental study of the equilibrium shapes of η′ and α precipitates in Mn-containing 7xxx Al-alloys

The addition of Mn to 7xxx series Al-alloys helps improve tensile properties owed to the presence of α precipitates (Al(Mn,Fe)Si, simple cubic, 50–200 nm, non-shearable) in addition to the η′ precipitates (Mg2Zn5−xAl2+x, hexagonal, 4–6 nm, shearable) commonly observed in the 7xxx series Al-alloys. The coexistence of multiple α and η′ variants, 24 for α and 4 for η′, coupled with their small size-scale, makes the experimental determination by x-ray diffraction (XRD) and scanning transmission electron microscopy (STEM) challenging. This work formulates a phase-field model to predict precipitate shapes in three-dimension (3D) using experimental characterization as inputs to create virtual precipitate cross-sections for use in morphological comparison with experimental 2D (S)TEM images. Based on the atomic structures and orientation relationships observed in the experiments, the lattice site correspondences between the matrix and the two precipitate phases are derived, which are required for the prediction of shapes of coherent precipitates. Systematic phase-field simulations are then carried out to document the 3D shapes for all possible variants, as well as the corresponding 2D cross-sectional shapes when observed parallel to low-index matrix planes. These 2D cross-sectional shapes are compared with high-angle annular dark-field STEM (HAADF-STEM) images, which demonstrates that the identification of Mn precipitate type is possible by such comparisons. This helps unravel some of the complications encountered when characterizing precipitate microstructures in Mn containing Al-alloys by STEM. Finally, the equilibrium shapes as a function of precipitate size and the effect of interfacial energy anisotropy are investigated.

Infrared reflection absorption spectroscopy of the adsorbed structures of a protic ionic liquid on the low-index planes of Pt

Modification with a protonic ionic liquid containing [7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD)][bis(pentafluoroethanesulfonyl)imide (beti)] enhanced the activities of the cathodic reactions of fuel cells (oxygen reduction reactions (ORR)) on Pt(111) and Pt(110), whereas it deactivated Pt(100). To elucidate the reaction mechanism, the ORR inhibiting species (PtOH) and the adsorption geometries of [MTBD][beti] on the low-index planes of Pt were studied using infrared reflection absorption spectroscopy (IRRAS). After modification with [MTBD][beti], the intensity of the bands representing PtOH decreased in the spectra of all the low-index planes. The adsorbed MTBD was tilted toward Pt(111) and vertically adsorbed onto Pt(110). On Pt(100), MTBD was adsorbed with its molecular plane parallel to the surface. Bands representing adsorbed beti were observed in the spectra of all surfaces. The increased ORR activities of the Pt(111) and Pt(110) surfaces were attributed to the decrease in PtOH formation after [MTBD][beti] modification and the low steric hindrance of the vertically adsorbed MTBD. Meanwhile, the deactivation of Pt(100) can be attributed to the increased steric hindrance of the parallel adsorption geometry of MTBD.

Oriented secondary magnetite micro-inclusions in plagioclase from oceanic gabbro

Abstract Plagioclase-hosted submicrometer to micrometer-sized oriented needle- and lath-shaped magnetite micro-inclusions with their elongation direction aligned parallel to the plagioclase [001] (PL[001]) direction were investigated using correlated optical, scanning electron, and scanning transmission electron microscopy. The PL[001] magnetite micro-inclusions formed from older generations of differently oriented magnetite micro-inclusions by recrystallization during hydrothermal alteration. Six orientation variants of PL[001] magnetite micro-inclusions occur, and they share the same shape orientation but differ in their crystallographic orientation relationships to the plagioclase host. The magnetite-plagioclase interfaces are facetted. High-resolution scanning transmission electron microscopy revealed that interface facets are aligned parallel to low-index lattice planes corresponding to oxygen layers of either magnetite or plagioclase. In addition, the linkage between prominent crystal structure elements of magnetite and plagioclase across the interfaces and accommodation mechanisms minimizing misfit between the two crystal structures were discerned. Combined evidence suggests that the shape and shape orientation, as well as the crystallographic orientation relationships between the magnetite micro-inclusions and the plagioclase host, are crystallographically controlled. The close crystal-structural link between magnetite precipitates and plagioclase host ensures a low-energy configuration driving recrystallization of older generations of differently orientated magnetite micro-inclusions into those that are aligned parallel to PL[001] and facilitates the underlying reaction kinetics. Due to their single to pseudo-single domain characteristics, the plagioclase-hosted magnetite micro-inclusions are particularly robust carriers of natural remanent magnetization. Recrystallization of differently oriented preexisting magnetite micro-inclusions into magnetite micro-inclusions with uniform shape orientation parallel to PL[001] has interesting consequences for the magnetic anisotropy of magnetite-bearing plagioclase grains.

MIDDLE RANGE ORDER IN GLASSES OF La2O3–Nb2O5–B2O3 AND BaO–Nb2O5–P2O5 SYSTEMS ACCORDING TO X-RAY TOTAL SCATTERING

We have obtained the X-ray total scattering patterns at wavelength 0.20735 ? and corresponding to them radial distribution functions (RDF) of electron density for glasses in the La2O3–Nb2O5–B2O3 and BaO–Nb2O5–P2O5 systems. The RDF demonstrate separate peaks at distances below ~1 nm which points on the middle range ordering in the considered glasses. The consideration of RDF for BaO–Nb2O5–P2O5 glasses system with high concentration of BaO show that the middle range order is caused by the polyhedra chains of ideal BaO crystal, and these chains does not belong to any low-index crystal plane. For La2O3–Nb2O5–B2O3 glasses system the polyhedra chains are observed which resemble those in the LaB3O6 crystal, with polyhedra bound through borate groups. For all considered glasses the niobium polyhedra does not form extended chains.

Crystal Structure Controls on Oriented Primary Magnetite Micro-Inclusions in Plagioclase From Oceanic Gabbro

Abstract Oriented needle-, lath- and plate-shaped magnetite micro-inclusions in rock forming plagioclase from mafic intrusive rocks, were investigated using correlated optical microscopy and scanning transmission electron microscopy. The magnetite micro-inclusions were analysed on cuts parallel and perpendicular to the inclusion–elongation directions. The crystal structures of the two phases are in direct contact along the interfaces. The shape, shape orientation and crystallographic orientation relationships between the magnetite micro-inclusions and the plagioclase host appear to be controlled by the tendency of the system to optimise lattice match along the interfaces. The elongation direction of the inclusions ensures good match between prominent oxygen layers in the magnetite and plagioclase crystal structures across the interfaces bounding the inclusions parallel to their elongation direction. In cross-section, additional modes of lattice match, such as the commensurate impingement of magnetite and plagioclase lattice planes along the interfaces, the parallel alignment of the interfaces to low-index lattice planes of magnetite or plagioclase, or the parallel alignment to low index lattice planes of both phases are observed, which appear to control the selection of interface facets, as well as the shape and crystallographic orientation relationships between magnetite micro-inclusions and plagioclase host. The systematics of the inclusion cross-sectional shapes and crystallographic orientation relationships indicate recrystallisation of magnetite with potential implications for natural remanent magnetisation of magnetite-bearing plagioclase grains.

Room-temperature plastic deformation of single crystals of α-manganese - hard and brittle metallic element

The deformation behavior of single crystals of α-manganese has been investigated by micropillar compression at room temperature as a function of crystal orientation and specimen size. When the specimen size is reduced to the micrometer-range, single crystals of α-manganese are found to plastically deform by dislocation motion at room temperature for the first time, accompanied by very high yield stresses of the range of 4–6 GPa. Slip along [111] and [001] are identified to operate for compression axis orientations near [001] and near [011] and [1¯11], respectively. Any low-indexed planes cannot be designated as the slip plane for both slip along [111] and [001], because of the significantly wavy nature of slip lines caused by the occurrence of frequent cross-slip. Slip along [111] tends to prefer the slip plane of {112} rather than {110}. Slip along [001], on the other hand, tends to occur on the maximum resolved shear stress plane. The 1/2[111] dislocation carrying slip along [111] moves as a perfect dislocation without dissociating into partials and does not have any preferred orientation. The [001] dislocation carrying slip along [001] also moves as a perfect dislocation without dissociating into partials. Although the Peierls stress for the motion of these dislocations must be very high, there seems no deep Peierls valleys along particular directions, unlike the screw direction for the 1/2[111] dislocation in body-centered cubic metals.

Effects of Hydrophobic Species on the Oxygen Reduction Reaction on the High-Index Planes of Pt3Fe

Pt3Fe(111), Pt3Fe(775) = 7(111)–(111), and Pt3Fe(544) = 9(111)–(100) electrodes show the highest activity in the low-index planes, n(111)–(111), and n(111)–(100) series of Pt3Fe, respectively. The surfaces of these electrodes were modified with hydrophobic species such as THA+, melamine, and ionic liquid ([MTBD][beti]), and the effects on the oxygen reduction reaction (ORR) were studied. All the hydrophobic species improved the ORR activity on all the electrodes examined. The ORR activity of Pt3Fe(111) in 0.1 M HClO4 containing 0.1 μM melamine was 2.1 times higher than that of Pt3Fe(111) without melamine, giving 39 times higher activity than that of bare Pt(111). The durability was improved on all the electrodes examined in melamine-containing solution.