Large Surface Roughness Research Articles

Highly Selective Production of C2+ Oxygenates from CO2 in Strongly Acidic Condition by Rough Ag‐Cu Electrocatalyst

AbstractThe acidic electrocatalytic conversion of CO2 to multi‐carbon (C2+) oxygenates is of great importance in view of enhancing carbon utilization efficiency and generating products with high energy densities, but suffering from low selectivity and activity. Herein, we synthesized Ag−Cu alloy catalyst with highly rough surface, by which the selectivity to C2+ oxygenates can be greatly improved. In a strongly acidic condition (pH=0.75), the maximum C2+ products Faradaic efficiency (FE) and C2+ oxygenates FE reach 80.4 % and 56.5 % at −1.9 V versus reversible hydrogen electrode, respectively, with a ratio of FEC2+ oxygenates to FEethylene up to 2.36. At this condition, the C2+ oxygenates partial current density is as high as 480 mA cm−2. The in situ spectra, control experiments and theoretical calculations indicate that the high generation of C2+ oxygenates over the catalyst originates from its large surface roughness and Ag alloying.

An In-Depth Exploration of Numerical Simulations for Stress Fields in Multi-Directional Rolling Processes

To address issues such as large surface roughness, coarse grains, and poor mechanical properties in low-carbon steel parts produced through wire arc additive manufacturing (WAAM), this paper proposes a method combining multi-directional incremental forming with the WAAM process. The additive manufacturing and cooling processes were simulated using the finite element software Abaqus to analyze the effects of multi-directional additive manufacturing on the stress field of the fabricated parts. The results indicate that after multi-directional incremental forming, the residual stress in the fabricated parts shifts from tensile stress to compressive stress, thereby reducing the risk of defects such as cracks. Moreover, the equivalent plastic strain of the processed parts increases, and the surface microhardness improves, with the most significant impact of multi-directional incremental forming observed in the contact area of the rolling head.

Utilization of molybdenum tailings as an alternative mineral filler in asphalt mastic: Rheological performance and environmental aspects

The generation and accumulation of molybdenum tailings (MT) have led to various environmental problems. This paper explores the feasibility of MT as a filler instead of limestone filler (LF) from the perspective of asphalt mastic. The physical and chemical properties of LF and MT are analyzed using Laser particle size, X-ray diffraction, X-ray fluorescence, and scanning electron microscopy tests. Four filler/asphalt weight (F/A) ratios (0.3, 0.6, 0.9, 1.2) are selected to prepare asphalt mastic. The rotational viscosity test, dynamic shear rheometer test as well as bending beam rheometer test, were conducted to study the rheological properties of mastics. Results show that physical interactions dominate the interaction between MT and asphalt. MT particles have large particle size, rough surface and tight internal structure. MT is conducive to bonding with asphalt. MT increased the viscosity, complex modulus, rutting factor and creep stiffness of asphalt. MT reduced the viscosity temperature sensitivity index, phase angle and creep rate. From the perspective of rheological properties, MT has great potential as filler to replace LF in asphalt mixture and reduce environmental pollution.

Highly Selective Production of C2+ Oxygenates from CO2 in Strongly Acidic Condition by Rough Ag-Cu Electrocatalyst.

The acidic electrocatalytic conversion of CO2 to multi-carbon (C2+) oxygenates is of great importance in view of enhancing carbon utilization efficiency and generating products with high energy densities, but suffering from low selectivity and activity. Herein, we synthesized Ag-Cu alloy catalyst with highly rough surface, by which the selectivity to C2+ oxygenates can be greatly improved. In a strongly acidic condition (pH=0.75), the maximum C2+ products Faradaic efficiency (FE) and C2+ oxygenates FE reach 80.4 % and 56.5 % at -1.9 V versus reversible hydrogen electrode, respectively, with a ratio of FEC2+ oxygenates to FEethylene up to 2.36. At this condition, the C2+ oxygenates partial current density is as high as 480 mA cm-2. The in situ spectra, control experiments and theoretical calculations indicate that the high generation of C2+ oxygenates over the catalyst originates from its large surface roughness and Ag alloying.

Investigation of open air and under water laser surface texturing on surface roughness and wettability of Al-Mg alloy

Aluminum-Magnesium (Al-Mg) alloy is widely used in aerospace and marine related applications due to its high corrosion resistance, tensile strength and ductility properties. However, due to hydrophilic nature, its applications are restricted in areas where water absorption may cause problems like corrosion. In this research work, high speed laser texturing was carried out on Al-Mg alloy (AA5754) to improve hydrophobic properties of the material surface. Four different types of pattern, namely lines, grids, concentric circles and concentric rectangles were created on the material surface using a nanosecond fiber laser. Scanning speed was varied at two levels i.e., 500 mm/s and 1000 mm/s. Line density of texture designs was also varied at two levels of 10 lines per mm and 15 lines per mm. The texturing process was carried out in two different processing environment namely open air and in underwater condition. Distilled water with 1 mm thickness above the surface was used during underwater texturing condition. Surface morphology, surface roughness and wettability of all the surfaces were studied for all the experimental conditions. It was observed that lower scanning speed of 500 mm/s resulted in higher values of surface roughness and contact angles. Also, larger texture density leads to lower surface roughness and contact angles for all the pattern designs. Among all the studied texture patterns, grid structures, textured at 500 mm/s of scanning speed resulted in largest surface roughness and surface hydrophobicity.

Excellent magnetic properties obtained in planar flow casting Fe-6.5 %Si steel via low strain cold-rolling and annealing

Planar flow casting (PFC) has been applied to prepare Fe-6.5wt. %Si ultra-thin ribbons with a strong 〈001〉 fiber texture. However, critical issues such as fine grain size and large surface roughness are vital to overcome. In this study, low strain cold-rolling and subsequent annealing are applied to planar flow casting Fe-6.5 %Si ribbons. Cold-rolling reduces surface roughness and introduces heterogeneous deformation in the ribbons. Recrystallization occurs preferentially in high deformed areas during annealing. Recrystallizing grains grow significantly by consuming neighboring deformed grains with fine size and 〈001〉 orientation, leading to greatly reduced iron loss. Thus, the ribbon annealed at 1000 ℃ exhibits the best combination of magnetic properties with B8 of 1.29 T and P2/5000 of 6.95 W/kg. The kinetics of recrystallization and grain growth are described along with the calculations of activation energies, which suggests the cold-rolled ribbon has a faster growth rate than the undeformed one. Two mechanisms, namely strain-induced boundary migration (SIBM) and thermo-induced boundary migration (TIBM), are used to explain the grain growth. SIBM is dominant at low temperatures while TIBM is dominant at high temperatures. This work presents a strategy to tailor the microstructures and properties of PFC-prepared alloys with fine grain.

Coupling effect of large deformation and surface roughness on dynamic frictional contact behaviors of hyperelastic material

Coupling effect of large deformation and surface roughness on dynamic frictional contact behaviors of hyperelastic material

Oil and gas development influences potential for dust emission from the Upper Colorado River Basin, USA

AbstractWind erosion and dust emission from drylands have large consequences for ecosystem function and human health. Wind erosion is naturally reduced by soil crusting and sheltering by non‐erodible roughness elements such as plants. Land uses that reduce surface roughness and disturb the soil surface can dramatically increase dust emission. Extraction of oil and gas is a common and growing land use in the western United States (US) that removes vegetation and other roughness elements for construction of well pads and unpaved access roads, resulting in thousands of small (1–4 ha), discrete patches of unprotected soil. Here, we use a satellite albedo‐based model to assess the effect of oil/gas activity on surface roughness in the Uinta‐Piceance Basin, an area of the Upper Colorado River Basin (UCRB) with dense oil and natural gas development and modelled how the change in surface roughness could impact aeolian sediment flux and dust emission. We also investigated how regional drought influences the response of surface roughness to well pads and access roads. Oil/gas activity reduced surface roughness and increased modelled aeolian sediment flux at the landscape scale across much of the study region, resulting in a modest increase of 10 139 kg of dust per year, which is small relative to dust loads from a single regional dust event observed in the region, but downwind impact could be significant. The magnitude of surface roughness reductions by oil/gas activity was generally consistent among land cover types. However, in parts of the basin that had high cover of annual forbs and grasses, oil/gas activity was associated with larger surface roughness and smaller potential dust emission. Drought decreased surface roughness across disturbed and undisturbed sites, but there was no interactive effect of oil/gas activity and drought on surface roughness. These results suggest that oil/gas activity may increase sediment fluxes and likely contributes to dust emission from landscapes in the UCRB. Understanding how drought and land use change contribute to dust emissions will benefit mitigation of undesirable impacts of wind erosion and dust transport.

Multichiral Mesoporous Silica Screws with Chiral Differential Mucus Penetration and Mucosal Adhesion for Oral Drug Delivery.

In the harsh gastrointestinal tract, helical bacteria with hierarchical chiral architectures possess strong abilities. Taking inspirations from nature, we developed a multichiral mesoporous silica nanoscrew (L/D-MCNS) as an efficient oral drug delivery platform by modifying the structural chiral silica nanoscrew (CNS) with L/D-alanine (L/D-Ala) enantiomers via the sequential application of a chiral template and postmodification strategies. We demonstrated that L-MCNS showed differential biological behaviors and superior advantages in oral adsorption compared to those of CNS, D-MCNS, and DL-MCNS. During the delivery, helical L/D-MCNS presenting distinctive topological structures, including small section area, large rough external surface, and a screw-like body, displayed multiple superiorities in mucus diffusion and mucosal adhesion. Meanwhile, the grafted chiral enantiomers enabled positive or negative chiral recognition with the biosystems. Once racemic flurbiprofen (FP) was encapsulated into the nanopores of L/D-MCNS (FP@L/D-MCNS), L/D-MCNS providing highly cross-linked and mesoscopic chiral nanochannels was beneficial for controlling the drug loading/release kinetics with chiral microenvironment sensitivity. Particularly, we noticed enantioselective absorption of FP in vivo, which could be attributed to the differential biological behaviors of L/D-MCNS. By simple design and regulation of the multilevel chirality of nanocarriers, L/D-MCNS can be employed for efficient oral drug delivery from the perspectives of material science, pharmacy, and bionics.

A Novel Approach to Surface Roughness Virtual Sample Generation to Address the Small Sample Size Problem in Ultra-Precision Machining.

Surface roughness is one of the main bases for measuring the surface quality of machined parts. A large amount of training data can effectively improve model prediction accuracy. However, obtaining a large and complete surface roughness sample dataset during the ultra-precision machining process is a challenging task. In this article, a novel virtual sample generation scheme (PSOVSGBLS) for surface roughness is designed to address the small sample problem in ultra-precision machining, which utilizes a particle swarm optimization algorithm combined with a broad learning system to generate virtual samples, enriching the diversity of samples by filling the information gaps between the original small samples. Finally, a set of ultra-precision micro-groove cutting experiments was carried out to verify the feasibility of the proposed virtual sample generation scheme, and the results show that the prediction error of the surface roughness prediction model was significantly reduced after adding virtual samples.

Investigating the CMAS corrosion resistance and thermal cycling failure behavior of porous thermal barrier coatings with different morphologies prepared by plasma spraying

This study investigates the influence of two-phase powder feeding spacing on the thermal cycling and CMAS corrosion resistance of the thermal barrier coatings (TBCs). Porous thermal barrier coatings with varying microstructures were prepared using the embedded micro agglomerated particle (EMAP) coating preparation method, which is based on conventional yttrium stabilized zirconia (YSZ) coatings. The method involved changing the powder feeding spacing. TBCs' failure mode and microstructure are investigated under complex service conditions. The corrosion resistance, thermal cycling life, hardness, and elastic modulus of TBCs are investigated by thermal cycling-CMAS experiments and isothermal corrosion tests. The EMAP coating has a good service life in the thermal cycling-CMAS tests, with a lower hardness, lower elasticit modulus and larger surface roughness than conventional coatings. This research aims to provide a strategy to optimize structure for TBCs with excellent comprehensive performance.

Morphology-transforming AuNPs-based fluorescent probe for ultra-low sensitive detection of levofloxacin in urine samples at pH 7.0 through excimer formation

Fluorescent metal nanoparticles (MNPs) have garnered considerable interest in the realm of healthcare applications. Within this domain, we present a novel fluorescent sensor: Pamoic acid (PA) functionalized excitation-dependent gold nanoparticles (PA@AuNPs), designed to ascertain levofloxacin (LF) concentrations in human urine samples under pH 7.0 conditions. The synthesis of PA@AuNPs was achieved via a chemical reduction method employing PA as both a reducing and stabilizing agent. Validation of the successful synthesis of PA@AuNPs was conducted utilizing a suite of analytical techniques including X-ray diffraction (XRD), ultraviolet–visible absorption spectroscopy (UV–Vis), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Microscopic examination via field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM) elucidated the spherical morphology of PA@AuNPs, with an average diameter ranging from 10 to 15 nm. Furthermore, atomic force microscopy (AFM) revealed an average surface roughness of 20.72 nm for PA@AuNPs. Thermal analysis results divulge that PA@AuNPs are highly stable up to 370 °C. The PA@AuNPs have shown more than 10-fold higher selectivity for LF in comparison with other commercially available antibiotics. The fluorescence emission intensity of PA@AuNPs (quantum yield (ΦF) 3.36 %) has shown enhanced redshift (436 → 497 nm; ∼61 nm) (λex 353 nm) upon the sequential addition of LF (0 → 100 µM) and achieved a lower detection limit (LoD = 36 nM; LoQ = 121 nM; Ka = 1.0457 × 104 M−1) with increased ΦF 18.96 %. This radiative process and fluorescence enhancement were confirmed by time-correlated single photon counting (TCSPC) measurement (4.89 → 5.36 ns). Interestingly, upon sensing LF, PA@AuNPs changed their morphology from spherical to octahedron and displayed an excimer formation through intermolecular π-π stacking. Furthermore, the stability of the complex, PA@AuNPs•LF which formed through coordination, by restoring the fluorescence intensity of PA@AuNPs•LF (turn on) in the presence of ethylenediamine tetraacetic acid (EDTA) (turn off) is demonstrated. The formation of the PA@AuNPs•LF complex was further confirmed by XRD analysis and FTIR spectroscopy. The HRTEM and FESEM validate that PA@AuNPs•LF have octahedral morphology with an average size of 20–30 nm, and the obtained moiré fringes in TEM images are due to the overlap of LF on the surface of PA@AuNPs. The AFM analysis divulges that PA@AuNPs•LF had a larger surface roughness (Sa = 26.91 nm). The experimentally attained zeta potential of PA@AuNPs (–12.6 mV) was further decreased (–17.6 mV) in the presence of LF, which confirms the interaction between PA@AuNPs and LF. The cell viability (82 %) in L929 Fibroblast cells augmented the biological applications of PA@AuNPs. The practicability of the fluorescent sensor probe was demonstrated in human urine samples with recovery ranges from 97.56 to 104.38 %.

Shear failure analysis of slip zone soil with different coarse particle shapes: Visualized shear test and PIV technology

Coarse particle shape in slip zone soil influences the mesoscopic structure of the soil, which in turn affects soil shear strength and failure behavior. In order to investigate the effect of particle shape on the shear characteristics of coarse–fine-grained mixed slip zone soil, three types of coarse particles (spheroidal, rounded, and angular) were selected for mixing and matching, and a total of 10 sets of medium-scale shear tests were designed for this paper. To quantify the shear deformation and failure process of slip zone soils, particle image velocimetry (PIV) technology and the hanging hammer method were used to obtain mesoscopic data of the soil (displacement vector data of soil particles and elevation data of the shear failure surface), which were used to calculate shear band thickness, shear dilatation, and roughness coefficient of the shear failure surface. The results indicate that coarse particle shape can considerably affect the macroscopic mechanical properties (internal friction angle and shear strength) and mesoscopic deformation characteristics (shear band thickness, shear dilatation, and shear surface morphology) of soils. Angular coarse particles have higher interlocking strength than spheroidal and rounded coarse particles, allowing angular coarse-grained slip zone soils to develop large shear band thickness and rough shear failure surfaces. In addition, mesoscopic damage analysis suggests that the damage rate of slip zone soils decreases with increasing coarse particle shape complexity. These findings enhance comprehension of the failure characteristics of soil-rock mixture slopes and serve as a good reference for the stability analysis of similar slopes.

Updates in the NCEP GFS PBL and Convection Models with Environmental Wind Shear Effect and Modified Entrainment and Detrainment Rates and Their Impacts on the GFS Hurricane and CAPE Forecasts

Abstract To reduce hurricane intensity bias, the NCEP Global Forecast System (GFS) planetary boundary layer (PBL) and convection schemes have been updated with a new parameterization for environmental wind shear and enhanced entrainment and detrainment rates with increasing PBL or subcloud mean turbulent kinetic energy (TKE) in their updraft and downdraft mass-flux schemes. Tests with the GFS show that the updated schemes significantly reduce the hurricane intensity bias by reducing the momentum transport in the mass-flux schemes. Along with the reduced intensity bias, the hurricane intensity and track errors have also been reduced. On the other hand, to reduce the PBL overgrowth over areas with a higher vegetation fraction or larger surface roughness, the entrainment rate in the PBL mass-flux scheme has also been increased with increasing vegetation fraction or increasing surface roughness. This entrainment rate increase has increased near-surface moisture, and as a result, helped to increase the underestimated convective available potential energy (CAPE) forecasts over the continental United States.

Organosilicon-Based Ligand Design for High-Performance Perovskite Nanocrystal Films for Color Conversion and X-ray Imaging.

Perovskite nanocrystals (PNCs) bear a huge potential for widespread applications, such as color conversion, X-ray scintillators, and active laser media. However, the poor intrinsic stability and high susceptibility to environmental stimuli including moisture and oxygen have become bottlenecks of PNC materials for commercialization. Appropriate barrier material design can efficiently improve the stability of the PNCs. Particularly, the strategy for packaging PNCs in organosilicon matrixes can integrate the advantages of inorganic-oxide-based and polymer-based encapsulation routes. However, the inert long-carbon-chain ligands (e.g., oleic acid, oleylamine) used in the current ligand systems for silicon-based encapsulation are detrimental to the cross-linking of the organosilicon matrix, resulting in performance deficiencies in the nanocrystal films, such as low transparency and large surface roughness. Herein, we propose a dual-organosilicon ligand system consisting of (3-aminopropyl)triethoxysilane (APTES) and (3-aminopropyl)triethoxysilane with pentanedioic anhydride (APTES-PA), to replace the inert long-carbon-chain ligands for improving the performance of organosilicon-coated PNC films. As a result, strongly fluorescent PNC films prepared by a facile solution-casting method demonstrate high transparency and reduced surface roughness while maintaining high stability in various harsh environments. The optimized PNC films were eventually applied in an X-ray imaging system as scintillators, showing a high spatial resolution above 20 lp/mm. By designing this promising dual organosilicon ligand system for PNC films, our work highlights the crucial influence of the molecular structure of the capping ligands on the optical performance of the PNC film.

Hydraulic-driven adaptable morphing active-cooling elastomer with bioinspired bicontinuous phases

The active-cooling elastomer concept, originating from vascular thermoregulation for soft biological tissue, is expected to develop an effective heat dissipation method for human skin, flexible electronics, and soft robots due to the desired interface mechanical compliance. However, its low thermal conduction and poor adaptation limit its cooling effects. Inspired by the bone structure, this work reports a simple yet versatile method of fabricating arbitrary-geometry liquid metal skeleton-based elastomer with bicontinuous Gyroid-shaped phases, exhibiting high thermal conductivity (up to 27.1 W/mK) and stretchability (strain limit >600%). Enlightened by the vasodilation principle for blood flow regulation, we also establish a hydraulic-driven conformal morphing strategy for better thermoregulation by modulating the hydraulic pressure of channels to adapt the complicated shape with large surface roughness (even a concave body). The liquid metal active-cooling elastomer, integrated with the flexible thermoelectric device, is demonstrated with various applications in the soft gripper, thermal-energy harvesting, and head thermoregulation.

Multifunctional aerogel with antibiofouling properties for efficient solar steam generation and seawater desalination

Water purification through solar steam generation is an emerging renewable technology with a massive capacity for freshwater generation. However, designing a multifunctional evaporating system with efficient solar-driven steam conversion along with seawater desalination is still a challenge for large scale freshwater generation. Herein, we propose a design for multifunctional photothermal aerogel containing Ag3VO4 nanoparticles incorporated in reduced graphene oxide with prominent characteristics of large surface area, higher porosity, and surface roughness. The proposed aerogel is fabricated via a facile method and can be used as an all-in-one system for water decontamination via solar steam generation, photocatalytic degradation/disinfection of organic pollutants and desalination of seawater simultaneously. The photothermal aerogel simply floats on air-water interface, with a higher flux of localized heat at the surface that efficiently promotes water evaporation at a rate of 2.1 kg/(m2 h). Moreover, the aerogel can denaturalize microorganism and desalinate seawater even under saline conditions. We anticipate that such an efficient and stable photothermal aerogel will offer a sustainable strategy for water purification via desalination, decomposition, and solar steam generation allowing us to address the current clean water crisis on a large scale.

Quantum Cascade Lasers Grown by Metalorganic Chemical Vapor Deposition on Foreign Substrates with Large Surface Roughness

The surface morphology of a buffer template is an important factor in the heteroepitaxial integration of optoelectronic devices with a significant lattice mismatch. In this work, InP-based long-wave infrared (~8 µm) emitting quantum cascade lasers with active region designs lattice-matched to InP were grown on GaAs and Si substrates employing InAlGaAs step-graded metamorphic buffer layers, as a means to assess the impact of surface roughness on device performance. A room-temperature pulsed-operation lasing with a relatively good device performance was obtained on a Si template, even with a large RMS roughness of 17.1 nm over 100 µm2. Such results demonstrate that intersubband-operating devices are highly tolerant to large RMS surface roughness, even in the presence of a high residual dislocation density.

Physicochemical properties and combustion kinetics of dried lignite

High water content in lignite leads to its low combustion efficiency, which hinders its large-scale utilization. Herein, lignite was dried under nitrogen atmosphere and changes in its pore structure and functional groups were analyzed. The combustion behavior of dried lignite was simulated using a thermogravimetric method. Moreover, the relationship between the lignite surface structure and combustion process of dried lignite was established based on grey correlation analysis. The results reveal that the pore structure of dried lignite was considerably damaged. At a drying temperature of 90 °C, the largest surface roughness and irregularity as well as the smallest the total pore volume and average pore diameter of lignite observed. As the drying temperature increased, the total pore volume first increased and then decreased; moreover, the average pore diameter increased from 13.55 to 15.75. With increasing drying temperature, the CH3/CH2 value of lignite initially increased up to 0.088 and then gradually decreased after 160 °C. At temperatures higher than 90 °C, the number of hydroxyl and carbonyl groups began to decrease. The worst and best combustion performances of lignite were observed when the drying process were conducted at 90 and 230 °C respectively. According to the results of grey correlation analysis, the average pore diameter exhibited the highest correlation coefficient (0.83) with the combustion performance of lignite. The drying process of lignite changes its average pore diameter; therefore, the combustion performance can be improved by adjusting the pore structure of lignite during the drying process. Furthermore, it is recommended to dry lignite at 230 °C to reduce energy loss during the drying and combustion processes and improve the utilization efficiency of lignite.

Nondestructive dielectric measurement method for orientation distribution of liquid crystal polymers film

Liquid crystal polymers (LCP) are widely used materials in 5G applications. The LCP films easily tend to form an uneven orientation distribution that degrades their service properties. However, tailoring its orientation distribution remains a challenge, primarily because traditional measurement methods are unable to non-destructively measure the orientation distribution of large-area LCP films attributed to penetration depth constraints or sample preparation requirements. Capitalizing on its inherent orientation-induced dielectric anisotropy, we propose a nondestructive dielectric measurement method for the orientation distribution of LCP film using an interdigital electrodes array. Compared to polarized FTIR and WAXS/SAXS, the dielectric method provides a universally applicable solution, even in intricate scenarios like regions with wrinkles in LCP films, films with substantial thickness, and those lacking large-scale structures. Moreover, the accurate measurement of orientation distribution confirms that the large surface roughness and significant variations in thickness distribution are attributed to the uneven orientation distribution. The findings provide a “visual window” for precisely tailoring the orientation structure of LCP films for 5G applications and beyond.