Low Roughness Research Articles

A novel approach to enhancing performance and endurance in GeS2 OTS devices using amorphous carbon doped W2N electrodes

Three–dimensional (3D) cross-point (X–point) memory has gathered interest for its fast data processing and high density, achieved by stacking memory with a selector device to prevent misinterpretation. Ovonic threshold switching (OTS) is a promising selector due to its reversible switching behavior. Although, OTS devices typically employ transition metal nitrides (TMN) such as TiNx, TaNx, and WNx for electrodes owing to their good stability, high melting points, and low resistivity, TMNs can diffuse and degrade device performance by recrystallizing with chalcogenide alloys. Amorphous carbon (a–C) can be a good alternative electrode material due to its low roughness, cost–effectiveness, high work function (WF), and excellent thermal stability. However, the high resistivity of a–C (∼ 150 mΩ–cm) increases threshold voltage (Vth), causing high power consumption. Therefore, combining both a–C and TMN materials can effectively obtain their advantages. This study explores the effect of varying a–C content in W2N electrodes on GeS2–based OTS selectors. The (W2N)1-xCx (0 ≤ x ≤ 0.25) electrodes were deposited using DC magnetron co–sputtering. The phase of (W2N)1-xCx (0 ≤ x ≤ 0.25) films transformed from polycrystalline to amorphous with increasing x. Devices with (W2N)1-xCx/GeS2/W2N structure showed decreased Vth and off current, improving from 4.8 to 3.8 V and 8.0–4.17 nA, respectively. The subthreshold slope, distance between traps, and interface trap density (Nit) were extracted using the Pool–Frenkel model. The reduced Vth may be attributed to a higher WF and lower Nit with increasing x. The device’s lifetime improved up to 1.0 × 109 pulses for the highest a–C content in (W2N)1-xCx (0 ≤ x ≤ 0.25) electrodes.

Electron transporting bilayers for perovskite solar cells: Spray coating deposition of c-TiO2/m-SnO2-quantum dots

Herein we present a comparative study among different spray-coated nanometric mesoporous electron transporting layers (ETLs) in perovskite solar cells (PSC), namely m-TiO2, m-SnO2 and m-SnO2 quantum dots (m-SnO2QDs). The solutions used for deposition were prepared from commercial pastes and colloidal suspensions for m-TiO2 and m-SnO2. For m-SnO2QDs in-house QDs solutions were prepared. The formamidinium-methylamonium-potassium (FAMA@10 K) has been used as light absorber material in the fabricated PSCs. The structural, compositional and morphological studies, correlated with the photovoltaic performance of PSCs, indicate that the m-SnO2 QDs layer is the best candidate among the three investigated mesoporous ETLs. Compared with the suspensions used for the other two ETLs, the in-house prepared SnO2 QDs solution presents smaller agglomerates of nanoparticles and results in the formation of a thinner, more uniform and compact mesoporous ETL. The FAMA@10 K perovskite deposited on m-SnO2 QDs ETL presents a lower roughness, better uniformity and a higher amount of PbI2. Our work unveils that the SnO2 QDs solution can be easily produced in laboratory and when is deposited as mesoporous scaffold in a PSC with FAMA@10 K perovskite, the power conversion efficiency increases up to 14.90 %, being with up to 27 % larger than in the PSCs with m-TiO2 and m-SnO2 ETLs prepared from commercial solutions. By modeling the J-V dynamic hysteresis with more than 90 % match between the calculated and experimental J-V data, for all three types of mesoporous ETLs, the relevant parameters that explain the hysteresis magnitude and account for ionic-induced recombination processes in PSCs were determined.

Constant period line gratings as a metric for patterning fidelity in electron beam lithography

As smaller critical dimensions of devices fabricated via electron-beam lithography (EBL) are achieved over large areas, the need for new metrology techniques follows. Large (cm × cm) substrates have traditionally been both time and labor intensive to measure using traditional techniques such as scanning electron microscopy (SEM) or atomic force microscopy. When optimizing an EBL process over large areas, stitch error must be eliminated to maximize feature placement fidelity. Simultaneously, traditional EBL requirements, such as low line-edge roughness, proximity effect correction, and appropriate write times, must be maintained. With this plethora of requirements, we propose a technique to characterize placement errors over large areas using interferometric measurements. This method, when combined with traditional techniques like SEM and optical microscopy, assesses the full domain of potential errors over large areas in a time- and cost-efficient manner. As a proof of concept, a set of five small format (5 × 10 mm2) gratings with an 855 nm period were written twice, each set produced under two different tool error conditions. We report on the efficacy of interferometric metrology to accurately assess feature placement errors and report measured groove displacement across all ten gratings.

Effects of Leafy Flexible Vegetation on Bed‐Load Transport and Dune Geometry

AbstractThe development of sustainable river management strategies requires knowledge of the effect of vegetation on hydrodynamics and sediment transport. To date, the complex physical processes involving the combined effects of leafy flexible vegetation and mobile bedforms are not completely understood. Most sediment transport models have been developed for bare bed conditions so that their performance in the presence of leafy flexible vegetation remains unclear. On the other hand, recently developed models consider vegetated conditions but they typically account only for the presence of rigid cylinders and in some cases scour at their base. For this purpose, laboratory experiments were conducted with mobile dune bed conditions and artificial flexible plants with varying Leaf Area Index to investigate the effect of flexible vegetation on bed morphology and sediment transport. Sediment transport rates and bedform characteristics such as height, wavelength and celerity, were measured in specifically designed experimental runs. The collected data show that the presence of leafy vegetation alters bed morphology, tending to reduce the average dune wavelength and leading to the formation of complex 3D geometries. Bed‐shear‐stress‐based models for predicting sediment transport were verified to be valid under conditions of low vegetation roughness density. On the contrary, the collected data emphasize that the measured bed‐load transport rate increased in the presence of leafy flexible vegetation with higher frontal area. Recent bed‐load models for vegetated channels provide a better interpretation for dense leafy vegetation but are less effective when predominant effects related to dunes are present.

A bio-inspired liquid-like smooth copolymer coating with superior biofouling resistance and drag reduction

The marine biofouling and fluid resistance have a detrimental impact on underwater vehicles. It is essential to develop functional material integrated with both antifouling and drag reduction effects for maritime transportation and navigation. Herein, to avoid the disadvantages of common slippery liquid-infused surfaces, such as the complexity of preparation micro/nanopores and the depletion of the lubricant layer, the novel liquid-like coating was fabricated by integrating the synthesized long chain organosilicon monomer (HPSM) to the self-polishing polymer chains. It is that the ingenious design integrated anti-fouling and drag reduction functions. The surface composition and structure, mechanical properties, antifouling and drag reduction properties of the coating were characterized by FT-IR, XPS, SEM, μ-PIV. These results indicated that the unique monomer HPSM endowed the coating with unique liquid-like properties, including special wettability, viscoelasticity and extremely low roughness. The flexibility of HPSM promoted the self-adaption ability of the coating in the seawater environment, which can effectively either reduce the fluid resistance when the fluid flowed through the surface or the adhesion strength of the biofouling, such as lots of protein (BSA) and alga (Porphyridium sp.and Navicula sp.). Moreover, the synergistic effect between liquid-like properties and the interface renewal behavior of self-polishing components further strengthened the antifouling performance of the coating. The marine field test further indicated the comprehensive anti-fouling performance and mechanical stability of the coating in practical application scenarios. This research provided a facile approach for preparing antifouling and drag-reduction coating. Therefore, it was believed to be a great inspiration for the design of functional coating against biofouling and drag reduction in the ship and marine industry field.

(Invited) Epitaxial Process Development and Challenges for Advanced SiGe BiCMOS

The performance of an HBT is primarily influenced by 1D dopant profile obtained by CVD epitaxy. Typically, three epitaxial layers are required to construct an HBT: the collector, the intrinsic base, and the emitter. Collector layer can be grown by either NSEG or selective epitaxy. While the NSEG process is cost effective, it results in autodoping. Switching to selective epitaxy can mitigate autodoping but must be controlled to minimize faceting. The intrinsic base is critical to device performance, with boron positioning being a key factor. Incorporating substitutional carbon atoms into the SiGe lattice significantly reduces boron diffusion. By switching from SiH4 to Si2H6, three times more substitutional carbon incorporation in SiGe without interstitial C atoms at 550 °C is achieved. Below 600 °C, the co-flow approach is ineffective, necessitating a cyclic deposition-etch (CDE) approach to maintain selectivity. Comparisons between CDE and single deposition-etch (DE) approaches show that CDE degrades the monocrystalline SiGeC:B layer, resulting in high RMS roughness and degraded morphology. In contrast, the DE approach shows promising results with lower RMS roughness and no significant morphological degradation. The last epitaxial layer discussed is the emitter. Current fabrication methods involve non-selective Si:As deposition at growth temperatures above 600 °C, resulting in polycrystalline Si:As deposition on dielectrics and monocrystalline Si:As growth on silicon. A novel process developed at 550 °C using Si2H6 as silicon precursor yields monocrystalline emitter by amorphous deposition on dielectrics followed by solid phase epitaxial regrowth. However, this process exhibits TED of arsenic, making it currently not viable.

Experimental study of wet and dry milling effect on surface roughness of TC4 titanium alloy

Titanium alloys are important engineering materials used in various industry areas, such as aviation, aerospace and medical devices. The surface roughness is a significant parameter for assessing the machining quality of titanium alloys. In this study, in order to compare the effects of dry and wet milling conditions on the surface roughness of titanium alloys, we established a test system to obtain the surface roughness, three-dimensional milling vibration and three-dimensional milling force signals. The gray correlation theory was applied to investigate the correlation between surface roughness and milling vibration or milling force under dry and wet milling conditions. Using the least squares method, the prediction models of surface roughness corresponding to dry and wet milling conditions were developed according to the features of vibration or force signals. Furthermore, the combined prediction models of surface roughness that integrate multiple signal features and milling parameters were established. The comparison results revealed that there was a stronger correlation between roughness and milling force, milling vibration in wet milling. Wet milling exhibited significantly lower roughness compared to dry milling under the same machining parameters, with up to a 59% reduction. The correlation coefficient of the wet milling model is as high as 0.95.

Evaluation of titanium dioxide and tantalum pentoxide nanoparticles for coating NiTi archwires in orthodontics: An in vitro study

Background: This study aims to enhance the biocompatibility of Nickel–Titanium (NiTi) alloy by developing a new coating using titanium dioxide (TiO2) and titanium pentoxide (Ta2O5) through direct current (DC) reactive sputtering technology. Materials and methods: Two distinct coating materials, namely, TiO2 and Ta2O5, were used to fabricate NiTi orthodontic archwires with improved surface properties. TiO2 nanoparticles, with thickness ranging from 21.90 nm to 31.93 nm, were deposited onto NiTi alloy substrates through DC reactive sputtering deposition under different power conditions. Results: X-ray diffraction and field emission scanning electron microscopy validated the uniformity and morphology of the coatings. Immersion tests in simulated body fluid (SBF) revealed significant hydroxyapatite layer growth on TiO2-coated NiTi, especially at a sputtering power of 240 W. Reduced nickel ion release was observed on TiO2 nanoparticles with a thickness of 21.90 nm at 50 W sputtering power compared with 31.93 nm-thick nanoparticles at 240 W. Ta2O5 thin films were deposited on NiTi substrates through DC magnetron reactive sputtering at ~100 °C with a deposition power of 50 W. Structural and morphological analyses through optical microscopy and X-ray diffraction, atomic force microscopy, and scanning electron microscopy revealed the homogeneity and low roughness of the coatings. Biocompatibility assessments in artificial saliva and SBF solutions established that Ta2O5-coated NiTi alloys exhibited superior electrochemical behavior, enhanced corrosion resistance, and diminished Ni ion release compared with uncoated specimens. Conclusion: TiO2 and Ta2O5 coatings not only improved the biocompatibility of NiTi orthodontic archwires but also presented a promising path for advanced biomedical applications. These coatings have potential in improving the cellular behavior and performance of NiTi-based orthodontic devices.

Neural Network Approach for Modelling and Compensation of Local Surface-Tilting-Dependent Topography Measurement Errors in Coherence Scanning Interferometry

The topography measurement accuracy of coherence scanning interferometry (CSI) suffers from the local characteristic of micro-structured surfaces, such as local surface slopes. A cylindrical reference artefact made of single-mode fiber with high roundness and low roughness has been proposed in this manuscript to traceably investigate the surface tilting induced measurement deviations using coherence scanning interferometry with high NA objectives. A feed-forward neural network (FF-NN) is designed and trained to model and thereafter compensate the systematic measurement deviations due to local surface tilting. Experimental results have verified that the FF-NN approach can well enhance the accuracy of the CSI for radius measurement of cylindrical samples up to 0.3%. Further development of the FF-NN for modelling of the measurement errors in CSI due to the optical properties of surfaces including areal roughness is outlined.

POSS and PAG Dual-Containing Chemically Amplified Photoresists by RAFT Polymerization for Enhanced Thermal Performance and Acid Diffusion Inhibition

A random copolymer (PTBM), utilized as deep ultra-violet (DUV) photoresist, was prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization with tert-butyl methacrylate (tBMA), methyl methacrylate (MMA), triphenylsulfonium p-styrenesulfonate (TPS-SS), and functional poly (sesquicarbonylsiloxanes) (POSS-MA) as the monomer components, and 4-cyano-4-[(dodecylsulfanylthiocarbonyl) sulfanyl]pentanoic acid (CDSPA) as the RAFT reagent. Fourier transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance (1H NMR) proved successful synthesis. Ultraviolet absorption spectroscopy (UV) analysis verified the transparency of the polymer in the DUV band. RAFT polymerization kinetics showed that the polymerization rate conformed to the first-order kinetic relationship, and the polymerization process exhibited a typical controlled free radical polymerization behavior. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and static thermo-mechanical analysis (TMA) showed that the incorporation of POSS groups improved the thermal properties of the copolymer. According to scanning electron microscopy (SEM) images, the copolymerization of photoacid monomers (TPS-SS) resulted in photoresist copolymers exhibiting good resistance to acid diffusion and low roughness.

INITIATED CHEMICAL VAPOR DEPOSITION (iCVD) OF POLY(ACRYLIC ACID): A COMPARISON BETWEEN CONTINUOUS AND CLOSED-BATCH iCVD APPROACHES

In this study, poly(acrylic acid) (PAA) thin films were deposited on silicon wafer and glass surfaces by initiated chemical vapor deposition (iCVD) method using di-tert-butyl peroxide (TBPO) as the initiator and acrylic acid (AA) as the monomer. During iCVD, two different precursor feeding approaches, namely continuous and closed-batch, were employed. The effects of substrate temperature and the precursor feeding approaches on the deposition rates and surface morphology of the films were investigated. The highest deposition rates for the continuous and closed-batch iCVD approaches were found as 26.1 nm/min and 18.6 nm/min, respectively, at a substrate temperature of 15 °C. FTIR analysis of the films deposited by both approaches indicated high structural retention of the monomer during the polymerization. AFM results indicated that, PAA thin films possessed low RMS roughness values of 2.76 nm and 1.84 nm using continuous and closed-batch iCVD, respectively. Due to the slightly higher surface roughness of the film deposited under continuous iCVD, that film exhibited a lower water contact angle of 16.1° than the film deposited in closed-batch iCVD. In terms of monomer utilization ratio, closed-batch system was found to be more effective, which may help to minimize the carbon footprint of iCVD process.

Enhanced optical gain assisted by the plasmonic effects of Au nanoparticles in Nd³⁺ doped TeO₂-ZnO waveguides produced with the pedestal architecture

Investigation of the signal enhancement of Nd3+ codoped TeO2-ZnO pedestal waveguides, at 1064 nm, due to Au nanoparticles deposited over the core is presented for the first time. Nd3+ doped TeO2-ZnO thin film was obtained by RF Magnetron Sputtering deposition. The resulting core with 500 nm height and widths in the 4–40 μm range, exhibited low roughness average in all area measured (0.48 ± 0.04) nm. Minimum propagation losses of 2.2 dB/cm were observed for waveguide width of 40 μm whereas an increase took place for smaller ones. Scanning electron microscopy (SEM) allowed the waveguide structure inspection and transmission electronic microscopy (TEM) the Au nanoparticles evaluation. The results showed that the Au nanoparticles contributed up to 75 % of relative gain enhancement, under 808 nm excitation. This increase was due to the local field growth in the proximity of the nanoparticles that enhances the density of excited Nd3+. The internal gain that considers the propagation losses reached positive values for larger core widths (above 8 μm).The present study opens possibilities for optical amplifiers with low propagation losses based on different metal-dielectric composites, as well as other waveguide-based devices.

Growth mechanism and performance of MAO-AO composite coating obtained by two-stage process

Titanium alloys, with the high specific strength and low elastic modulus, are currently the research focus of many applications. Various surface treatments have been applied with the intention of improving their wear and corrosion resistance. Micro-arc oxidation (MAO) technology originated from anodic oxidation (AO) technology, which has the advantages of simple process, high efficiency and environmentally friendly electrolyte. However, due to the micro-arc discharge effect, MAO coatings inevitably show the characteristic of high porosity. In this study, post-treatment of MAO coatings using AO was proposed to obtain a composite coating with both high hardness and low roughness and porosity thereby compensating for the defects of MAO coatings. After preparation, each sample was analyzed and characterized. The results indicated that AO was main conducted in the discharge channel of MAO coating and an amorphous phase coating with the matrix oxide as main component was grown in situ. The composite coating showed a slight increase in thickness and significant reduction in roughness than MAO coating and with superior wear and corrosion resistance. In conclusion, this study provides new idea and data support for improving the performance of MAO coatings, which is expected to be widely used in the field of surface treatment.

Approaching Angstrom-Scale Resolution in Lithography Using Low-Molecular-Mass Resists (

Resists that enable high-throughput and high-resolution patterning are essential in driving the semiconductor technology forward. The ultimate patterning performance of a resist in lithography is limited because of the trade-off between resolution, line-width roughness, and sensitivity; improving one or two of these parameters typically leads to a loss in the third. As the patterned feature sizes approach angstrom scale, the trade-off between these three metrics becomes increasingly hard to resolve and calls for a fundamental rethinking of the resist chemistry. Low-molecular-mass monodispersed metal-containing resists of high atom economy can provide not only very high resolution but also very low line-width roughness without sacrificing sensitivity. Here we describe a modular metal-containing resist platform (molecular mass <500 Da) where a molecular resist consists of just two components: a metal and a radical initiator bonded to it. This simple system not only is amenable to high-resolution electron beam lithography (EBL) and extreme ultraviolet lithography (EUVL) but also unites them mechanistically, giving a consolidated perspective of molecular and chemical processes happening during exposure. Irradiation of the resist leads to the production of secondary electrons that generate radicals in the initiator bonded to metal. This brings about an intramolecular rearrangement and causes solubility switch in the exposed resist. We demonstrate record 1.9-2.0 nm isolated patterns and 7 nm half-pitch dense line-space features over a large area using EBL. With EUVL, 12 nm half-pitch line-space features are shown at a dose of 68 mJ/cm2. In both of these patterning techniques, the line-width roughness was found to be ≤2 nm, a record low value for any resist platform, also leading to a low-performance trade-off metric, Z factor, of 0.6 × 10-8 mJ·nm3. With the ultimate resolution limited by instrumental factors, potential patterning at the level of a unit cell can be envisaged, making low-molecular-mass resists best poised for angstrom-scale lithography.

Carbon Thin-Film Electrodes as High-Performing Substrates for Correlative Single Entity Electrochemistry.

Correlative methods to characterize single entities by electrochemistry and microscopy/spectroscopy are increasingly needed to elucidate structure-function relationships of nanomaterials. However, the technical constraints often differ depending on the characterization techniques to be applied in combination. One of the cornerstones of correlative single-entity electrochemistry (SEE) is the substrate, which needs to achieve a high conductivity, low roughness, and electrochemical inertness. This work shows that graphitized sputtered carbon thin films constitute excellent electrodes for SEE while enabling characterization with scanning probe, optical, electron, and X-ray microscopies. Three different correlative SEE experiments using nanoparticles, nanocubes, and 2D Ti3C2Tx MXene materials are reported to illustrate the potential of using carbon thin film substrates for SEE characterization. The advantages and unique capabilities of SEE correlative strategies are further demonstrated by showing that electrochemically oxidized Ti3C2Tx MXene display changes in chemical bonding and electrolyte ion distribution.

Efficient oil spill cleanup from water: Investigating the effectiveness of a sustainable anti-swelling hydrogel for rapid water repellency and oil absorption

Considering the significant harm caused to aquatic ecosystems and marine life by oil spills and the discharge of oily wastewater, there is a pressing need to address this issue to protect our environment and prevent the wastage of valuable resources. We introduced a two-step approach to create an anti-swelling, water-repellent sorbent using a green polysaccharide called gum gellan, functionalized with Octadecyl trichlorosilane (OTS) through dip coating method. Natural gums like gellan have high absorption capability due to their large surface area. However, they are hydrophilic, which means they can only absorb water. This property makes them unsuitable for oil spill applications. To make gum gellan suitable for oil spill applications, we have modified it in this study. We have introduced a material called octadecyltrichlorosilane, which has low surface energy and hierarchical roughness. This modification changes the wettability of gellan from hydrophilic to hydrophobic/oleophilic, allowing it to absorb oil and repel water. The sorbent is analyzed using several techniques, such as FTIR, XRD, TGA, FE-SEM, BET, Raman, EDX, and H1-NMR. The hydrophobic sorbent obtained demonstrates low density, high surface area, and high porosity. These characteristics give it excellent floatability and immediate and exceptional selectivity for absorbing oil from water. Additionally, it does not absorb any detectable amount of water. The sorbent exhibited a water contact angle (WCA) of 140 ± 3 ° and an oil contact angle (OCA) of 0° for various oils and organic solvents. It has rapid oil absorption capacity of 3.72 g/g for diesel, and can be easily recovered after use. The BET analysis revealed that after the modification with OTS, the sorbent's total surface area increased from 0.579 m2/g to 4.713 m2/g. This indicates that the OTS modification greatly enhances the surface area and pore volume of the, thus improving its ability to absorb oil. This sorbent efficiently separates oil-in-water emulsions, both surfactant-stabilized and surfactant-free, achieving over 90% separation through gravity alone. Moreover, the sorbent can sustain its wettability even under harsh environmental conditions, including exposure to acids, alkalis, and salts. The absorption data predominantly aligned with the pseudo-2nd-order model. Thus, this sorbent provides a cost-effective alternative for efficiently absorbing and separating oil-water emulsions in households and industries.

The key role in the structure and properties of a novel CrNiTiMo high-entropy alloys films prepared by magnetron sputtering: Bias voltage

In this study, CrNiTiMo high-entropy alloys films were prepared on 304 stainless steel and silicon wafer substrates by direct current magnetron sputtering and the effects of bias voltages (0 to −200 V) on microstructure, chemical composition, hardness and corrosion resistance were investigated. The results showed that the surface of the CrNiTiMo HEAs films exhibited equiaxed nanoparticles and are composed of uniformly distributed Cr, Ni, Ti, and Mo elements. Meanwhile, the films developed a columnar structure and formed a biphasic structure with body-centered cubic solid solution and amorphous phases. The roughness decreased and then increased with increasing bias voltage, and the film deposited at −50 V had the lowest roughness (1.02 ± 01 nm), which also had a maximum hardness of approximately 9.52 ± 0.2 GPa and a maximum elastic modulus of approximately 187 ± 6 GPa. In addition, all films showed better corrosion resistance compared to 304 stainless steel substrates at 3.5 wt% NaCl solution. The corrosion current density (icorr) of the films decreased and then increased with increasing bias voltages and reached the lowest icorr of about 2.49 × 10−8A/cm2, indicating that the films deposited at a bias voltage of −50 V had the best corrosion resistance. These was attributed to the formation of the passivation films mainly composed of TiO2 and Cr2O3 and the improvement of the surface quality of the film as well as the refinement of the columnar structure and particles.

Roughness constant selection for atmospheric boundary layer simulations using a k-ω SST turbulence model within a commercial CFD solver

Transit of an atmospheric boundary layer (ABL) profile within computational fluid dynamics (CFD) simulations is often hindered through unintended streamwise gradients in the flow resulting in ABL inhomogeneity. Within Reynolds-Averaged Navier–Stokes (RANS) turbulence modeling in Ansys Fluent, user-defined wall functions are not available for the k–ω class of RANS models as a remedy to this problem. Instead, the practitioner is required to use the sand–grain roughness property for ground surface roughness calibration, and specify a roughness height and roughness constant, Cs, accordingly. To-date, no clear guidance on their selection is available that can accommodate both high and low roughness terrains. To overcome this, a straightforward and practical calculation is presented for the roughness constant based on the standard wall function implementation. When this calculation is synthesized with other best-practice guidelines, it is possible to reliably model transiting ABL profiles based on wind-tunnel data whilst minimizing effects due to ABL inhomogeneity.

Surface Modification of Feldspathic Ceramic Used for Minimally Invasive Restorations: Effect of Airborne Particle Type on the Surface Properties and Biaxial Flexural Strength.

This study aimed to evaluate the effect of airborne particle abrasion with different particles on the surface free energy, roughness, and biaxial flexural strength of a feldspathic ceramic by comparing it with hydrofluoric acid etching, the standard surface treatment, and polishing. Square-shaped feldspathic ceramic specimens (12 mm × 12 mm × 1.2 mm) were divided into subgroups as airborne particles abraded with alumina (AO3a, AO3b, AO25, AO50a, AO50b, AO90, AO110a, AO110b, AO120a, and AO120b), silica (SO50a, SO50b, SO100, and SO100/200), or nutshell granule (NS100/200), hydrofluoric acid etched, and polished (n = 12). Surface free energy (n = 5), roughness (n = 5), biaxial flexural strength (n = 12), and Weibull moduli (n = 12) were investigated. Data were evaluated with 1-way ANOVA and Tukey HSD tests, and possible correlations were investigated with Pearson's correlation (α = 0.05). SO100/200 mostly had lower surface free energy (p ≤ 0.011), and polishing and etching led to higher surface free energy than AO3a, AO3b, and AO120a (p ≤ 0.031). Polished, SO100, and SO50b specimens mostly had lower roughness and AO125 had the highest roughness (p ≤ 0.029). SO100/200 mostly had lower biaxial flexural strength (p ≤ 0.041), and etched specimens had higher biaxial flexural strength than AO120a, AO120b, and SO50b (p ≤ 0.043). AO3b had the highest (33.56) and AO120b had the lowest (11.8) Weibull modulus. There was a weak positive correlation between the surface free energy and the biaxial flexural strength (r = 0.267, p = 0.011). A larger particle size mostly resulted in higher roughness, which was also affected by the particle shape. Most of the test groups had similar biaxial flexural strength to that of the hydrofluoric acid-etched group. Therefore, for tested feldspathic ceramic, airborne particle abrasion with tested parameters may be a suitable alternative without causing any further damage.

Direct electrodeposition on conductive polymer structures for microwave device manufacturing

This work introduces a method that merges Additive Manufacturing (AM) with Direct Electrodeposition to efficiently produce microwave (MW) components. Using material extrusion (MEX) with conductive polymers and an improved direct copper deposition approach, this method streamlines the manufacturing process, bypassing the need for intermediate conductive layers. By minimizing the distance electrical currents travel within the conductive polymer, we obtain homogeneous copper deposits directly on the polymer with low roughness and excellent adhesion. The practical application of our technique is showcased through the radiative performance evaluation of a millimeter wave horn antenna manufactured using our approach, demonstrating similar electromagnetic performances with respect to a commercially available reference. The method proposed in this paper results in lightweight, material-efficient components with increased design flexibility, opening up possibilities for rapid prototyping and fabrication of new MW devices.