Peculiar Surface Research Articles

Using bearing ratio curves to quantify the surface roughness parameters of fly ash-teff straw ash-based geopolymer mortars

Considering the prominent attributes of surface roughness parameters, the closer their solutions are to real surfaces, the more appropriate they are for civil engineering applications. One of the steps that can be considered for such applications is to incorporate the bearing ratio curve (BRC) parameters in the study of civil engineering materials. In this research, the bearing ratio curves have been used for the first time to quantify the surface roughness attributes of fly ash-teff straw ash-based geopolymer mortars. For various cases, the roughness parameters in the V-group are compared with the roughness parameters in the Rk group, which contributes to the attractiveness of this research. The fly ash-teff straw ash-based geopolymer mortar specimens in this study are dominated by smooth surfaces, as evidenced by the Rvk and Rpk values of less than 0.21 μm for all specimens. The study highlights that if such surfaces are to be used in mortar-to-mortar bonding, imposed surface roughness could be required to enhance the bond strength of the layers. In addition, the results indicate that critical roughness parameters can be identified from the bearing ratio curves when a surface is undergoing roughness transformations. These findings provide a step towards the understanding of BRC parameters for fly ash-teff straw ash-based geopolymer mortar surfaces. Overall, the approach demonstrated in this study could also accelerate and promote the surface roughness characterisation for geopolymer mortars and could be extended to unlock peculiar surface roughness properties for other civil engineering materials.

Topological signatures of triply degenerate fermions in Heusler alloys: an ab initio study

Triply degenerate nodal point (TP) fermions, lacking elementary particle counterparts, have been theoretically anticipated as quasiparticle excitations near specific band crossing points constrained by distinct space-group symmetries instead of Lorentz invariance. Here, based onfirst-principlescalculations and symmetry analysis, we demonstrate the presence of TP fermions in Heusler alloys. Furthermore, we predict that these Heusler alloys are dynamically stable, exhibiting TP fermions along four distinctC3axes in the F-43m space group. We show thatα-LiCaPdSb harbours peculiar Fermi arcs and surface states on the (111) and (001) crystal facets, owing to the coexistence of threefold rotational and time reversal symmetry. More interestingly, a modest tensile strain can increase the distance of fermions along the Γ-Lhigh symmetric line by as much as 21.10%, which give rise to measurable Fermi arcs. Furthermore, we investigate non-trivial topological insulator phase inβ-LiCaPdSb, by changing the chemical environment through placing transition metal atoms at various Wyckoff positions. Theβ-LiCaPdSb harbour a semi-metallic nature, and by breaking cubic symmetry, it undergoes a transition from semi-metal to a non-trivial topological insulator. In addition, for the first time, rare-earth LaPtBi half-Heusler alloy is examined under strain to uncover multiple band inversions associated with the TP fermionic phase. The observed multiple band inversion is entirely unaffected by spin-orbit coupling. We show that the LaPtBi compound hosts TP fermions, which are linked to aZ2topological invariant. Remarkably, with clear band crossings and multiple band inversion, we point out the possibilities of the LaPtBi for displaying a rich topological phase diagram. Our work provides a prototype material platform for experimental detection through angle-resolved photoemission spectroscopy or scanning tunnelling spectroscopy and practical spintronic applications.

Comparative investigation of composition, microstructure and property influences on electrocatalysis of two representative cathodes: BaCo0.4Fe0.4Zr0.1Y0.1O3-δ versus Ba0.5Sr0.5Co0.8Fe0.2O3-δ

BaCo0.4Fe0.4Zr0.1Y0.1O3-δ (BCFZY) and Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) perovskites are two representative high-performance cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Here, symmetric cell tests demonstrate that polarization resistance values of BCFZY cathode are only 0.21–0.29 times those of BSCF cathode at 740–660 °C, and 0.21–0.26 times those of BSCF cathode at the oxygen partial pressures of 1.00–0.10 atm. Distribution of relaxation times (DRT) is applied to detect individual electrode processes overlapped in impedance spectra, which finds that the dominant processes of oxygen dissociation, subsequent species transfer and reduction on BCFZY cathode are superior to those of BSCF cathode. By temperature-programmed desorption of oxygen (O2-TPD), thermal expansion coefficient (TEC) measurements, scanning electron micrograph (SEM) and energy dispersive spectra measurements, the strong oxygen combination ability with higher activation energy of oxygen desorption (Ed = 84 kJ/mol), peculiar surface state with evident nano-particle structure, more matchable TEC (19.0 × 10-6 K−1) and excellent interfacial connection with the electrolyte are observed on BCFZY cathode to account for its distinctive catalysis, as compared to BSCF cathode (Ed = 68 kJ/mol, TEC = 24.2 × 10-6 K−1).

Experimental and numerical determination of the fatigue notch factor in as‐built wire arc additive manufacturing steel components

AbstractParts manufactured by wire arc additive manufacturing (WAAM) are characterized by a peculiar surface morphology, namely, surface waviness, that negatively affects the fatigue performance. To exploit the full potential of WAAM and minimize the need for postproduction work, it is crucial to utilize the components in the as‐built state. This is because conventional machining techniques, typically employed for postprocessing operations, severely curtail the freedom of geometry of the components. This study focuses on an experimental and numerical characterization of the notch effect of the surface waviness for an AISI 308 LSi stainless steel. This is done by quantifying the fatigue notch factor in a probabilistic fashion, considering the results of ad‐hoc designed fatigue tests. A finite element model is developed by considering a 3D scan of the geometry of WAAMed plates, allowing to determine the theoretical stress concentration factor. The fatigue notch factor is also estimated from the numerical model by making use of the gradient correction according to the FKM guidelines. To validate the numerical approach, test data produced for different testing conditions are correlated by using the local stress approach, showing that classical methods are also applicable to additive manufactured parts.

Lateral Piezoelectricity of Alzheimer's Aβ Aggregates.

Alzheimer's disease (AD) is the most frequent neurodegenerative disorder in the elderly aged over 65. The extracellular accumulation of beta-amyloid (Aβ) aggregates in the brain is considered as the major event worsening the AD symptoms, but its underlying reason has remained unclear. Here the piezoelectric characteristics of Aβ aggregates are revealed. The vector piezoresponse force microscopy (PFM) analysis results exhibit that Aβ fibrils have spiraling piezoelectric domains along the length and a lateral piezoelectric constant of 44.1 pC N-1. Also, the continuous sideband Kelvin probe force microscopy (KPFM) images display that the increment of charge-induced surface potential on a single Aβ fibril is allowed to reach above +1700mV in response to applied forces. These findings shed light on the peculiar mechano-electrical surface properties of pathological Aβ fibrils that exceed those of normal body components.

Tuning Mg Doping and Features of Bone-like Apatite Nanoparticles Obtained via Hydrothermal Synthesis.

Nanocrystalline apatites have been intensively studied for decades, not only for their well-known mimesis of bone apatite but also for applicative purposes, whether as biomaterials for skeletal repair or more recently for a variety of nanomedical applications enabled by their peculiar surface characteristics. Particularly, ion-doped apatites are of great interest because the incorporation of foreign ions in the composition of apatite (nano)crystals alters the bulk and surface properties, modifying their ability to interact with the external environment. This is clearly seen in the physiology of bone tissue, whose mineral phase, a low crystallinity apatitic phase, can dynamically exchange ions with cells, thus driving bone metabolism. Taking bone mineral as a model, the present work describes the development of Mg-doped hydroxyapatite nanoparticles, exploiting hydrothermal synthesis to achieve extents of Mg2+ doping hardly achieved before and using citrate to develop stable apatite colloidal dispersions. Morphological and physicochemical analyses, associated with in-depth investigation of ions populating the apatitic lattice and the nonapatitic surface layer, concurred to demonstrate the cooperative presence of Mg2+ and citrate ions, affecting the dynamic ion retention/release mechanisms. Achieving high Mg2+ doping rates and understanding how Mg doping translates into surface activation of apatite-based nanoparticles is expected to foster the design of novel smart and tunable devices, to adsorb and release ionic species and cargo molecules, with potential innovations in the biomedical field or even beyond, as in catalysis or for environmental remediation.

Synthesis of InZrOx nanosheets and its application in CO2 hydrogenation to methanol

Synthesis of methanol via CO2 hydrogenation is a very important reaction. In recent years, the In2O3 based catalysts were proved to be a sort of promising catalysts to accelerate this reaction, which have aroused extensive attention. However, design of novel In2O3 based catalysts that can efficiently produce methanol from CO2 hydrogenation at low temperature is still in great need. Herein we fabricated the InZrOx nanosheets via a simple solvothermal method, which had peculiar surface structure and plenty of oxygen defects. The InZrOx nanosheets displayed excellent low temperature catalytic performance in a slurry reactor. The methanol selectivity (90 %) and activity (1.4 mmol gIn-1h−1) were achieved at 180 °C, which are 2.3 and 1.6 times than that of the counterpart nanoparticles, respectively. Water as a clean and cheap reaction solvent played a crucial role, which participated in the kinetic process of the catalysis. The particular catalyst structure and the solvent effect of water accounting for the outstanding reaction results.

Multiplicative generalized tube surfaces with multiplicative quaternions algebra

Along with other types of calculus, multiplicative calculus brings an entirely new perspective. Geometry now has a new field as a result of this new understanding. In this study, multiplicative differential geometry was used to explore peculiar surfaces. Multiplicative quaternions are also used to depict surfaces. Additionally, multiplicative differential geometry was used to generate the accretive surface subject, which is a developing subject. The derived surfaces' perspective silhouette curve equation is provided. The Bishop multiplicative frame was also established and applied when expressing surfaces along with these. Finally, the surfaces and perspective silhouette curves were visualized using Maple, and the equations were obtained.

Realization of Jackiw–Rebbi zero-energy modes at photonic crystal domain walls: Emergence of polarization-indiscriminate surface states

The Jackiw–Rebbi model is a relativistic quantum model credited with the theoretical predictions of zero-energy bound states and charge fractionalization prior to the discovery of topological insulators and the fractional quantum Hall effect. In this work, we demonstrate a photonic equivalent of the Jackiw–Rebbi model by resorting to photonic crystal band structure engineering. Specifically, our photonic realization employs two spatial inversion symmetric binary photonic crystals exhibiting complementary signs of differential effective mass parameter (δm) for their second bandgaps. Their concatenation manifests a step discontinuity in the spatial profile of the effective mass parameter, forming a domain wall at the photonic crystal interface. Upon analyzing the reflectance spectra of the concatenated photonic crystal structure, we find a midgap surface state localized at this domain wall. Furthermore, much in agreement with the Jackiw–Rebbi zero-energy solution, the materialized photonic surface state also exhibits a zero-energy character in a differential energy space corresponding to the δm parameter, which has been quantified experimentally. Crucially, the conceived zero-energy mode amounts to the observation of a peculiar surface state with polarization-indiscriminate dispersion that can help realize all-angle polarization neutral optics.

Contact tracing of binary stars: Pathways to stellar mergers

Stellar mergers are responsible for a wide variety of phenomena such as rejuvenated blue stragglers, highly magnetised stars, spectacular transients, iconic nebulae, and stars with peculiar surface chemical abundances and rotation rates. Before stars merge, they enter a contact phase. Here, we investigate which initial binary-star configurations lead to contact and classical common-envelope (CE) phases and assess the likelihood of a subsequent merger. To this end, we computed a grid of about 6000 detailed 1D binary evolution models with initial component masses of 0.5 − 20.0 M⊙ at solar metallicity. Both components were evolved, and rotation and tides were taken into account. We identified five mechanisms that lead to contact and mergers: runaway mass transfer, mass loss through the outer Lagrange point L2, expansion of the accretor, orbital decay because of tides, and non-conservative mass transfer. At least 40% of mass-transferring binaries with initial primary-star masses of 5 − 20 M⊙ evolve into a contact phase; > 12% and > 19% likely merge and evolve into a CE phase, respectively. Because of the non-conservative mass transfer in our models, classical CE evolution from late Case-B and Case-C binaries is only found for initial mass ratios qi < 0.15 − 0.35. For larger mass ratios, we find stable mass transfer. In early Case-B binaries, contact occurs for initial mass ratios qi < 0.15 − 0.35, while in Case-A mass transfer, this is the case for all qi in binaries with the initially closest orbits and qi < 0.35 for initially wider binaries. Our models predict that most Case-A binaries with mass ratios of q < 0.5 upon contact mainly get into contact because of runaway mass transfer and accretor expansion on a thermal timescale, with subsequent L2-overflow in more than half of the cases. Thus, these binaries likely merge quickly after establishing contact or remain in contact only for a thermal timescale. On the contrary, Case-A contact binaries with higher mass ratios form through accretor expansion on a nuclear timescale and can thus give rise to long-lived contact phases before a possible merger. Observationally, massive contact binaries are almost exclusively found with mass ratios q > 0.5, confirming our model expectations. Because of non-conservative mass transfer with mass transfer efficiencies of 15 − 65%, 5 − 25%, and 25 − 50% in Case-A, -B, and -C mass transfer, respectively (for primary-star masses above 3 M⊙), our contact, merger, and classical CE incidence rates are conservative lower limits. With more conservative mass transfer, these incidences would increase. Moreover, in most binaries, the non-accreted mass cannot be ejected, raising the question of the further evolution of such systems. The non-accreted mass may settle into circumstellar and circumbinary disks, but could also lead to further contact systems and mergers. Overall, contact binaries are a frequent and fascinating result of binary mass transfer of which the exact outcomes still remain to be understood and explored further.

Mode-dependent magnonic noise

The performance of magnonic devices such as converters, switches, and multiplexers greatly depends on magnonic noise. While a peculiar discrete magnonic noise has been previously reported, the sources of underlying magnon dynamics occurring in high-magnon density conditions have not been clarified. Here, zero-span measurements of the spectrum analyzer were recorded to accurately detect magnonic noise as a fluctuation of the spin-wave amplitude. The results of low-frequency magnonic noise demonstrated a spin-wave mode dependency, indicating the existence of a peculiar magnon surface state. Furthermore, the energy thresholds of four-magnon scattering and autooscillation were determined using magnonic white noise. The noise data obtained in this study can help promote theoretical and experimental research on magnons.

Unique ghost surface phonon polaritons in biaxially hyperbolic materials.

We predicted peculiar ghost surface phonon polaritons in biaxially hyperbolic materials, where the two hyperbolic principal axes lie in the plane of propagation. We took the biaxially-hyperbolic α-MoO3 as one example of the materials to numerically simulate the ghost surface phonon polaritons. We found three unique ghost surface polaritons to appear in three enclosed wavenumber-frequency regions, respectively. These ghost surface phonon polaritons have different features from the surface phonon polaritons found previously, i.e., they are some hybrid-polarization surface waves composed of two coherent evanescent branch-waves in the α-MoO3 crystal. The interference of branch-waves leads to that their Poynting vector and electromagnetic fields both exhibit the oscillation-attenuation behavior along the surface normal, or a series of rapidly attenuated fringes. We found that the in-plane hyperbolic anisotropy and low-symmetric geometry of surface are the two necessary conditions for the existence of these ghost surface polaritons.

Review of the Priapulida of New Zealand with the description of a new species

ABSTRACT The number of priapulid species occurring in the waters around New Zealand is uncertain, as up to four species were reported and three of them declared as doubtful. Our investigation of 28 specimens from the NIWA collection (Auckland, New Zealand) document three species. Three specimens of Priapulus tuberculatospinosus come from circum-antarctic waters. Around New Zealand, Priapulopsis australis is most abundant, less abundant is Priapulus tuberculatospinosus. Two specimens are described here as a new species, Priapulopsis papillatus sp. nov., as they deviate in several characters from the other species. These characters are the shape of the first ring teeth, presence of large, abundant and regularly arranged trunk papillae, a peculiar surface structure of the trunk and peculiarities in the posterior ringpapillae. All species are described by scanning electron microscopy and several new observations are reported. In addition to postlarval and adult specimens, 15 larval specimens are reported. The larvae resemble very much the previously described larvae of Priapulopsis bicaudatus and therefore likely belong to the genus Priapulopsis.

Supramolecular systems based on chitosan and chemically functionalized nanocelluloses as protective and reinforcing fillers of paper structure

Supramolecular systems based on chitosan and cellulose nanofibers (CNFs) with a different surface modification (TEMPO-oxidation and carboxymethylation) were investigated and utilized for the functional consolidation of paper. Prior to the paper consolidation, the interactions between chitosan and CNFs dispersed in aqueous solvent were studied. It was detected that the peculiar surface functionalization of nanocellulose is crucial to control the chitosan/CNFs electrostatic attractions and, consequently, the entropic/enthalpic contributions and the stoichiometry of the biopolymer adsorption onto the cellulose nanofibers. Dynamic Light Scattering and rheological experiments revealed that the presence of biopolymeric chains on the CNFs surface favors the entanglement and the aggregation between the nanofibers reinforcing their network. It was observed that chitosan and nanocellulose exhibit synergetic effects on the paper consolidation in terms of reinforcing action, surface hydrophobization and enhancement of the fire-resistance. In conclusion, this paper demonstrates that the electrostatic interactions between chitosan and functionalized nanocellulose drive the formation of hybrid fillers suitable for paper consolidation. Chitosan coated CNFs possess an improved capacity to penetrate the paper structure causing an enhancement of the mechanical resistance and surface hydrophobization. Moreover, chitosan/CNFs create a protective barrier for heat transfer that prevents the paper combustion.

Surface morphology control of multifunctional biomimetic silica particles: Interfacial properties and optical effects

Hierarchically structured biomimetic particles are functionally tunable yet structurally robust, which are versatile building blocks with a broad range of applications from biological systems to optoelectronic devices. Herein, we propose a facile and effective, scalable strategy to fabricate multifunctional biomimetic silica particles through surface morphology control. The various shapes of biomimetic silica particles possessing the surface structure of lotus leaves, as well as the form of raspberries and tori were readily achieved by varying the ratio of methyltrimethoxysilane and tetraethoxysilane precursors. Subsequent Ostwald ripening resulting from the differences in the reaction rate of dual precursors and thermodynamic stability of the initially formed particles yielded a variety of surface structures. Further, surface wettability can be controlled depending on the peculiar surface morphology of biomimetic silica particles. The biomimetic silica particle with rough and corrugated wrinkles similar to the surface of a lotus leaf afforded excellent superhydrophobicity and oleophobicity, and simultaneously provided intriguing optical properties including soft-focus and near-infrared-blocking effects. Our controlled approach opens a new way to fabricate mutifunctional biomimetic particles with a wide range of potential applications in water-repellent, antigravity water delivery, surface reflection control, and IR blocking materials.

Anomalous Diamagnetic Torque Signals in Topological Nodal-Line Semimetal NaAlSi

In topological materials, peculiar surface states protected by crystal symmetries have attracted great interest because of the possibility of unprecedented correlation with superconductivity. A topological nodal-line semimetal with a layered structure, NaAlSi shows moderately anisotropic bulk superconductivity with Tc ≅ 7.0 K. The magnetic torque curves as a function of the field angle in the superconducting state are found to show two distinct diamagnetic signals; a large broad signal arising from bulk superconductivity and a small sharp signal observed only in magnetic fields nearly parallel to the layers. The upper critical field of the bulk superconductivity follows an anisotropic 3D model with a small anisotropic factor of ∼4. A possible scenario is that the sharp signal is due to highly 2D superconductivity with a similar Tc, whose thickness is only several times of the c-axis lattice constant (0.736 nm). The band structure calculations show the presence of large Fermi lines on the (001) plane, mainly formed by the surface Si p bands. The sharp diamagnetic torque signal could arise from the (001) surface superconductivity.

Morphometric parameters of the relief and drainage network of a tropical subbasin

This research analyzed the morphological/morphometric parameters of the relief and drainage network of the Formiga River subbasin, southern Minas Gerais State, Brazil. This study identified and examined the influences of control mechanisms in the development of current configurations. The methodology was based on the application of indices and parameters: (1) slope length (Hack's Sl); (2) normalized slope index (ksn); (3) river hierarchy; (4) drainage density; (5) hydrographic density; (6) sinuosity index; (7) density of structural lineaments; (8) transverse topographic symmetry factor; (9) asymmetry factor of drainage basins; (10) topographic profiles transverse to the valleys; (11) relief ratio; (12) roughness index; (13) roughness concentration index; (14) compactness coefficient; (15) circularity index and (16) form factor. The results indicated 3 sectors of the subbasin with distinct geomorphic behaviors, which resulted in peculiar surface structures and divergent current dynamics. The subbasin presents physical evidence that demonstrates and corroborates strong tectonic and structural control in the development of the current drainage network and relief. Human action has also affected, from the construction of dams, the dynamics of the lower course of the river, drowned by the reservoir of the hydroelectric plant of Furnas.

PH Effects in a Model Electrocatalytic Reaction Disentangled.

Varying the solution pH not only changes the reactant concentrations in bulk solution but also the local reaction environment (LRE) that is shaped furthermore by macroscopic mass transport and microscopic electric double layer (EDL) effects. Understanding ubiquitous pH effects in electrocatalysis requires disentangling these interwoven factors, which is a difficult, if not impossible, task without physical modeling. Herein, we demonstrate how a hierarchical model that integrates microkinetics, double-layer charging, and macroscopic mass transport can help understand pH effects of the formic acid oxidation reaction (FAOR). In terms of the relation between the peak activity and the solution pH, intrinsic pH effects without consideration of changes in the LRE would lead to a bell-shaped curve with a peak at pH = 6. Adding only macroscopic mass transport, we can already reproduce qualitatively the experimentally observed trapezoidal shape with a plateau between pH 5 and 10 in perchlorate and sulfate solutions. A quantitative agreement with experimental data requires consideration of EDL effects beyond Frumkin correlations. Specifically, the peculiar nonmonotonic surface charging relation affects the free energies of adsorbed intermediates. We further discuss pH effects of FAOR in phosphate and chloride-containing solutions, for which anion adsorption becomes important. This study underpins the importance of a full consideration of multiple interrelated factors for the interpretation of pH effects in electrocatalysis.

Biopolymer Gels as a Cleaning System for Differently Featured Wooden Surfaces.

The cleaning of some wooden artefacts can be challenging due to peculiar surface roughness and/or particular finishing treatments that favour the deposition of dirt and contaminants. The most common cleaning system used by conservators is agar gel, characterized by its rigidity and brittleness, which challenges the cleaning of rough and irregular surfaces typical of most wooden artefacts. In this work, alginate crosslinked with calcium (CA) and konjac glucomannan crosslinked with borax (KGB) gels were proposed to solve this issue. They were prepared and applied to smooth- and rough-surfaced mock-ups replicating wooden musical instruments' surfaces that had been subsequently covered by artificial soiling and sweat contaminants. The mechanical properties of CA and KGB gels, including their stability over a 60-day storage time, were evaluated by a texture analyzer, while cleaning efficacy was analytically evaluated by non-invasive X-ray fluorescence mapping and profilometric investigation. CA gel appeared to have a higher tensile strength and elongation at break. KGB gel was shown to be soft and resilient, indicating its suitability for cleaning rough surfaces. After repeating the cleaning application three times on the rough-surfaced mock-ups, both the CA and KGB gels were shown to have cleaning efficacy. The results obtained with CA and KGB were compared with those from the Agar application.

Understanding surface charge effects in electrocatalysis. Part 2: Hydrogen peroxide reactions at platinum

Electrocatalytic activity is influenced by the surface charge on the solid catalyst. Conventionally, our attention has been focused on how the surface charge shapes the electric potential and concentration of ionic reactant(s) in the local reaction zone. Taking H2O2 redox reactions at Pt(111) as a model system, we reveal a peculiar surface charge effect using ab initio molecular dynamics simulations of electrified Pt(111)-water interfaces. In this scenario, the negative surface charge on Pt(111) repels the O–O bond of the reactant (H2O2) farther away from the electrode surface. This leads to a higher activation barrier for breaking the O–O bond. Incorporating this microscopic mechanism into a microkinetic-double-layer model, we are able to semi-quantitatively interpret the pH-dependent activity of H2O2 redox reactions at Pt(111), especially the anomalously suppressed activity of H2O2 reduction with decreasing electrode potential. The relevance of the present surface charge effect is also examined in wider scenarios with different electrolyte cations, solution pHs, crystal facets of the catalyst, and model parameters. In contrast with previous mechanisms focusing on how surface charge influences the local reaction condition at a fixed reaction plane, the present work gives an example in which the location of the reaction plane is adjusted by the surface charge.