Search Results (211)

Peri-implantitis treatment is challenging because of the complex micro- and nanostructured topography of implant surfaces. No standard debridement protocol exists. In this study, we compared five debridement methods used on heavily contaminated titanium implants that were explanted due to peri-implantitis. Twenty-five explanted implants (five per group) were treated with a carbon fiber ultrasonic insert, a polyetheretherketone (PEEK) ultrasonic insert, a rotating titanium brush, an erbium, chromium-doped yttrium, scandium, gallium, and garnet (Er,Cr:YSGG) laser, or an erbium-doped yttrium, aluminum, and garnet (Er:YAG) laser. Five pristine implants were used as controls. Surface morphology was assessed by scanning electron microscopy (SEM). The Modified-Implant Debridement Visual Index (M-IDVI) was used to assess the debridement effectiveness according to SEM images. Surface elemental composition was assessed for atomic percentage (at. %) of carbon, titanium, oxygen and nitrogen using energy-dispersive X-ray spectroscopy (EDS). Mechanical methods were more effective at removing debris than laser methods. The titanium brush showed the lowest residual debris (2.33 ± 0.33) and the greatest reduction in surface carbon (Δ = −7.77 at. %). Surface titanium increased after debridement for all methods except for Er,Cr:YSGG (Δ = −5.9 at. %). Er:YAG best preserved SLA microtopography but exhibited a lower debridement efficacy (3.27 ± 0.83) than mechanical methods. No method resulted in a pristine surface. Full article

This study presents a green-intensified system for the production of bio-based polyurethane foam using waste cooking oil (WCO) as the primary polyol source. The experimental setup was specifically designed to apply the concept of green intensification by integrating cavitation energy generated through ultrasonic irradiation with a high-shear mixing system. This hybrid approach facilitates the effective mixing of WCO-based bio-polyol with isocyanate, enhancing the reaction during foam formation. An ultrasonic atomizer was employed to convert water into a fine mist, which was then introduced into the reaction mixture using a controlled air blower. The misted water serves as an eco-friendly blowing agent, improving its dispersion within the polyol matrix. The results indicate that this method prolongs gel time, suggesting a more controlled and gradual blowing reaction. Furthermore, the combined use of ultrasonic irradiation and high-shear mixing significantly reduced foam density and produced a finer, more uniform cellular structure. These findings demonstrate that ultrasonic-assisted misting and emulsification not only enhance process efficiency but also contribute to the environmentally sustainable synthesis of bio-polyurethane foam. Full article

This study aims to demonstrate the feasibility of controlling particle size through a mathematical model in the design of industrially applicable ultrasonic spray nozzles by utilizing the vibrational characteristics of piezoelectric ceramics. A piezoelectric ceramic composition with a low sintering temperature and excellent thermal stability (Curie temperature above 300 °C) was developed and used as a ceramic vibrator. Furthermore, the resonance frequency and nozzle displacement were calculated using the COMSOL program and applied to a mathematical model to design an ultrasonic nozzle capable of producing a spray particle diameter of approximately 30 μm. The designed ultrasonic nozzle was fabricated, and its spray characteristics were analyzed. The consistency of the spray characteristics was examined by comparing them with the mathematical model based on changes in ultrasonic nozzle length, resonance frequency, and fluid viscosity. When the ultrasonic nozzle horn length was 22 mm, the resonance frequency was found to be 42.1 kHz, and at a flow rate of 65 mL/min. the average spray particle size was approximately 30–40 μm, indicating fine and uniform particles. In addition, it can be seen that as the length of the nozzle horn increases, the resonance frequency decreases, reducing the supply energy delivered to the liquid, and the particle size increases as shown in the mathematical analysis. The theoretical separation energy required to atomize pure water at a flow rate of 65 mL/min. is 2100 J, which was found to be greater than all energy loss occurring during the atomization process. However, it can be seen that as the length of the ultrasonic nozzle increases, the maximum atomization volume increases, and as viscosity increases, the energy required to separate a single atomized particle becomes greater. Full article

Ultra-precision machining of ferrous alloys remains challenging because conventional diamond tools suffer severe thermochemical wear, whereas ultrasonic vibration-assisted cutting requires complex and costly equipment. This study investigates single-crystal sapphire as an alternative cutting-tool material for ultra-precision machining of both non-ferrous and ferrous metals. A sapphire tool was fabricated from a polished wafer, laser-shaped into an equilateral triangular insert, vacuum-brazed onto a tungsten carbide carrier, and finished by ultra-fine grinding to yield a well-defined cutting edge. Ultra-precision turning experiments were conducted on copper and 420 stainless steel using a Moore Nanotech 350FG lathe, and the performance of the sapphire tool was benchmarked against conventional diamond (copper) and cubic boron nitride (CBN) tools (stainless steel) under comparable cutting conditions. Surface roughness (Ra) and topography were characterized using an optical surface profiler, while scanning electron microscopy and atomic force microscopy were employed to assess tool wear and cutting-edge geometry. The sapphire tool produced mirror-like surfaces with average surface roughness (Ra) values of 6.4 nm on copper and 39.1 nm on 420 stainless steel, compared with 1.3 nm for diamond on copper and 92.9 nm for CBN on stainless steel. Across both materials, sapphire generated regular, stable tool marks and exhibited minimal wear, with no catastrophic edge degradation or clear evidence of severe chemical interaction with the steel workpiece. These results demonstrate that sapphire is a viable tool material for extending diamond turning-level surface quality to stainless steel without ultrasonic assistance. Full article

Purpose: This study provides a comparative evaluation of surface changes in BioHPP materials under routine professional hygiene procedures, which is recommended by dentists, twice a year. BioHPP is a polyetheretherketone polymer used in prosthetic dentistry as a frame material. The aim was to investigate whether routine dental cleaning procedures such as ultrasonic scaling and brushing affect the surface proprieties of prosthetic BioHPP restorations. This study was conducted to evaluate the surface properties of different restorations based on BioHPP (veneered with composite resin and polished) after brushing and ultrasonic scaling exposure. Materials and Methods: The BioHPP specimens were divided into three groups. The first group (marked BioHPP) served as a baseline reference for assessing the effect of different surface processing approaches, and no further treatment was applied. The specimens in the second group (BioHPP-P) were polished, while the specimens in the third group (BioHPP-C) were veneered with composite resin. Group BioHPP-P and BioHPP-C of samples was divided into three subgroups: 0—no treatment, 1—exposed to tooth brushing, 2—exposed to ultrasonic scaling. Untreated samples (subgroup 0) served as controls for evaluating treatment-related changes within groups 2 and 3. The surface morphology was investigated by atomic force microscopy (AFM). The structure of samples was analyzed using the XRD technique, and the surface wettability was evaluated. Results: The surface roughness of the samples was evaluated via root mean square (RMS) parameter. Baseline BioHPP specimens exhibited higher roughness values compared to the other analyzed groups. The roughness of the non-treated specimens (0) decreased in the line 59.18→28.84→14.51 nm. Treatment of the samples by brushing and ultrasonic scaling was associated with an increase in surface roughness. Variations in water contact angle values were observed. However, no consistent treatment-related trend could be established. Conclusions: Composite veneered BioHPP showed a tendency toward higher surface resistance to brushing and ultrasonic scaling. These findings should be interpreted within the limitations of an in vitro descriptive study. Full article

To address the difficulty of simultaneously achieving effective heat dissipation and adequate humidification in open-cathode air-cooled proton exchange membrane fuel cells (PEMFCs) under medium and high power operation, this study proposes a hydrothermal management strategy based on coordinated ultrasonic atomization humidification and fan speed regulation. A three-dimensional single-cell multiphysics model is developed and validated using a 300 W experimental platform. The effects of atomization frequency and water temperature on stack performance and internal hydrothermal distribution are systematically investigated. Results show that ultrasonic atomization provides inlet precooling, latent heat absorption, and active region humidification, thereby improving hydrothermal uniformity within the stack. Under the optimal condition of 100 kHz and 55 °C, the peak stack power increases by 21.0% to 319.00 W, while voltage consistency and surface temperature uniformity are also improved. Analysis based on the Stokes number and Dalton’s law of partial pressures indicates that the optimum results from a balance between suppressing droplet agglomeration and inertial deposition, and limiting oxygen dilution caused by excessive water vapor. The proposed strategy provides a compact and practical approach for improving the stability, uniformity, and efficiency of air-cooled PEMFCs. Full article

In this study, the microstructure and mechanical properties of ultrasonic welded joints between large-diameter aluminum wire and Cu (Ni-plated copper) terminals were systematically investigated, to reveal the underlying fracture mechanisms. The cross-sectional morphology, interfacial microstructure, and mechanical properties of the two types of welded joints are investigated. The results indicate that ultrasonic welding produces well-structured Al-Cu and Al-Ni joints. Under the same welding process parameters, the Al-Cu joint exhibits many pores, while the Al-Ni joint has no pores in its microstructure. The interfacial region of the Al-Cu joint presents various morphologies, such as flat bonding, interlocking, and eddy current patterns, whereas the Al-Ni joint interface is flat. No significant atomic diffusion phenomenon occurs between the interfaces of the two types of joints. The tensile strength of the Al-Cu joint is 53 MPa, with fracture modes including ductile fracture and brittle fracture, whereas the tensile strength of the Al-Ni joint is 50 MPa, with a failure mode of pull-out fracture. In working conditions requiring ultrasonic welding of aluminum and copper, nickel-plated copper can be used as a substitute for copper to prevent electrochemical corrosion between aluminum and copper. Full article

The exceptional stability of C-F bonds renders PFAS highly persistent in aqueous environments, posing significant challenges for conventional treatment technologies. While plasma-based technologies show promise, their efficiency is often limited by poor gas–liquid mass transfer in bulk liquid. Here, an in-house constructed ultrasonic atomization–dielectric barrier discharge (UEN-DBD) system was developed to promote PFAS degradation under non-thermal plasma conditions. Ultrasonic atomization generated microdroplets, which promoted PFAS enrichment at the surface of microdroplets and facilitate interactions with plasma-generated reactive species. Using perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS) as model compounds, degradation behavior was evaluated over an initial concentration range of 0.01–1.0 ppm. At 0.01 ppm, degradation efficiencies of 96.06% for PFOA and 94.86% for PFOS were achieved within 5 min. Electron paramagnetic resonance (EPR) spectroscopy confirmed the formation of oxidative radicals (·OH) and suggested a mixed redox environment involving reactive species, potentially including superoxide (O₂·⁻) or hydrated electrons (e_aq⁻), in the discharge-treated system. High-resolution mass spectrometry results are consistent with a stepwise chain-shortening pathway dominated by successive –CF₂– scission, while fluoride-release measurements provided supporting evidence for partial defluorination. These findings advance the understanding of plasma-assisted PFAS degradation at the gas–liquid interface and provide a basis for the further development of plasma-assisted PFAS treatment strategies. Full article

For the first time, hybrid nanocomposites based on poly(2,5-dichloro-3,6-bis(phenylamino)-p-benzoquinone) (PCPAB) and multi-walled carbon nanotubes (MWCNTs) were obtained and the influence of the preparation method on their structure and functional properties was demonstrated. The nanocomposites were obtained both by ultrasonic mixing of PCPAB and MWCNTs, and via in situ oxidative polymerization of CPAB in the presence of MWCNTs or MWCNTs with the addition of ZnO. The formation of hybrid nanocomposites occurs due to non-covalent interaction (π-stacking) between the graphene structures of the MWCNT surface and the phenyl rings of PCPAB. It was found that during the in situ oxidative polymerization of CPAB in the presence of MWCNTs, the growth of polymer chains occurred in close proximity to the filler surface, which led to the formation of a polymer coating. ZnO particles, localized on MWCNTs, on the one hand, prevent their aggregation, and on the other hand, create additional polymerization reaction centers due to the coordination of the Zn-O bond at the H and O atoms of the monomer. An increase in the concentration of reaction centers as a result led to a 2–2.5-fold reduction in the induction polymerization period. According to SEM data, in this case, a more ordered and denser polymer layer is formed due to intermolecular complexation between the main and side chains of the growing polymer with the participation of Zn²⁺ ions formed as a result of the transformation of ZnO to ZnCl₂ in the acidic reaction medium of polymerization. The results of the study of the frequency dependences of conductivity indicate a hopping mechanism of conductivity of nanocomposites. The electrical conductivity of nanocomposites depends on their production method and the MWCNT content and varies between 0.5 and 1.1 S∙cm⁻¹, which is 6–12 times higher than the conductivity of the original polymer. Thermogravimetric analysis revealed that the nanocomposites exhibit enhanced thermal stability compared to PCPAB. The best results were shown by nanocomposites with a higher content of MWCNTs, for which the residual mass at 450 °C was 51–53%. Full article

Cemented carbides are essential in applications requiring exceptional hardness and wear resistance. However, the reliance on cobalt as a binder raises concerns related to cost, supply security, and health. High-entropy alloys (HEAs) are promising cobalt-free binders offering favorable mechanical properties and potential grain-growth control. This work presents a new approach for the development of Co-free WC-based cemented carbide employing an HEA binder designed through CALPHAD-guided simulations. An optimized composition corresponding to Al5Cr5Cu10Fe35Mn10Ni35 (at%) alloy is predicted to be FCC-dominant with minimal σ-phase formation and good compatibility with WC. A preliminary batch of powder of the proposed binder was produced by blending elemental powders, arc remelting, and ultrasonic atomization, yielding predominantly spherical particles with a dendritic microstructure. WC–HEA composites (WC–12 wt% HEA) were then prepared by ball milling, pressing, vacuum sintering, and sinter-HIP for a first evaluation of the microstructure and achievable hardness. The microstructure exhibited residual porosity without significant WC grain coarsening. XRD analyses showed the dominant presence of WC, along with FCC and M₃W₃C phases (M mainly Fe and Mn), indicating thermal interaction between the binder and WC. Despite these effects, the composite achieved a hardness of 1913 HV and retained a fine WC grain size (0.86 μm). The proposed design approach allowed the definition of a promising Co-free binder composition based on HEA with the expected microstructure, which will need further evaluation, especially aimed at investigating toughness properties as a function of the WC content. Full article

Sustainable feedstock management remains a major challenge in laser beam powder bed fusion (PBF-LB), where conventional reuse strategies are typically limited to sieving and blending rather than full material regeneration. Ultrasonic atomization (UA) offers a fundamentally different powder production route based on capillary-wave instabilities induced at the surface of a molten metal by high-frequency vibrations. In contrast to turbulence-driven atomization, droplet formation in UA is primarily governed by ultrasonic frequency and intrinsic thermophysical properties of the melt, enabling quasi-deterministic particle formation with high sphericity and reduced satellite formation. In this study, ultrasonic atomization was investigated as a closed-loop route for converting PBF-LB-manufactured 316L stainless steel parts into reusable powder. Printed rods were remelted and atomized under controlled variation of electric current and vibration amplitude. The resulting powders were characterized in terms of morphology, internal microstructure, particle size distribution, chemical composition, and gas impurity content. UA produced highly spherical particles with reduced internal porosity and improved flowability compared to the initial gas-atomized powder, while preserving the principal alloying elements. An increase in oxygen content was observed after recycling, attributed to selective high-temperature oxidation under residual oxygen in nominally inert conditions. The results establish a mechanistic framework for transforming consolidated PBF-LB material into secondary feedstock and identify key parameters governing structural and compositional stability in closed-loop recycling. Full article

A sequenced ultrasonic atomization coupled with a pyrolysis process is developed to synthesize a series of cross-scale (Co/Cu)-NC catalysts. The catalysts demonstrate high metal utilization efficiency with a metal loading of 22.45 ± 0.07 wt%. Electrochemical evaluations for the oxygen reduction reaction (ORR) suggest that the best (Co/Cu)-NC catalysts are prepared with a Co/Cu ratio of 1/1 and a calcination temperature of 800 °C, which achieve a half-wave potential of 0.87 V and an electrochemical impedance spectroscopy semicircle radius as low as 30 ohms. Linear sweep voltammetry measurements indicate that (Co/Cu)-NC catalysts exhibit the highest current density. Under a potential of −0.73 V versus the reversible hydrogen electrode, (Co/Cu)-NC catalysts demonstrate long-term stability with the CO Faradaic efficiency of about 70% for catalyzing carbon dioxide reduction reaction (CO₂RR). Overall, the above metrics identify CoCu-800 as the optimal bifunctional catalyst among the tested samples for ORR and CO₂RR under the investigated conditions. Full article

Nickel–titanium (NiTi) shape memory alloys offer transformative functionality for biomedical and aerospace systems, yet their adoption in additive manufacturing (AM) remains constrained by powder reactivity, compositional sensitivity, and the high energy of feedstock production. This work establishes a unified, data-driven evaluation of how powder-state evolution during reuse and ultrasonic plasma atomization (UPA) affects both functional behavior and environmental performance. Virgin, reused, and UPA-recycled NiTi powders were systematically characterized based on particle-size distribution (PSD), SEM morphology, sphericity, oxygen content (ONH), and differential scanning calorimetry (DSC), and these results were coupled with a process-level life-cycle assessment (LCA) spanning cradle-to-gate feedstock generation. Reused powder showed finer but broadened PSD, surface oxidation, and elevated transformation temperatures; these degradation mechanisms limited its reuse despite reducing energy demand by ~30% relative to virgin powder. UPA provided a more effective regeneration pathway: UPA-recycled NiTi recovered high sphericity and smooth particle surfaces while lowering cradle-to-gate energy from 100 ± 10 to 50 ± 5 MJ·kg⁻¹ (≈50%) and reducing CO₂-equivalent emissions by ≈45%, with ~95% material recovery. Although the UPA condition exhibited a higher oxygen content in this study due to system-level atmosphere limitations, prior work indicates that optimized inert-gas control can suppress oxidation, suggesting clear avenues for improvement. Sustainability Index analysis confirmed UPA as the most favorable route, integrating reductions in energy demand and emissions with recovery of powder morphology and reconditioning of thermal transformation behavior. More broadly, the ability of UPA to promote compositional and microstructural redistribution highlights its potential to deliberately re-tune or “reprogram” transformation temperatures for application-specific requirements when alloying and processing atmospheres are carefully managed. Full article

Copper (Cu), silver (Ag), and copper–silver (Cu–Ag) powders were synthesized using ultrasonic spray pyrolysis (USP) combined with hydrogen-assisted reduction in order to examine how key processing parameters influence particle characteristics. The effects of reduction temperature, gas atmosphere, and precursor molar ratio on particle morphology, size distribution, and elemental composition were systematically investigated. Aqueous precursor solutions of copper nitrate trihydrate and silver nitrate were atomized in a USP reactor and thermally treated under hydrogen-containing or argon atmospheres at temperatures between 500 and 700 °C. The resulting powders were characterized by scanning electron microscopy (SEM), particle size analysis using ImageJ, and energy-dispersive X-ray spectroscopy (EDS). The results showed that both temperature and gas atmosphere strongly affected particle formation. Hydrogen-assisted synthesis promoted efficient reduction and high metal purity but was associated with increased particle coalescence, whereas argon atmospheres yielded finer and more uniform particles through thermally driven decomposition. In the case of Cu–Ag powders, the precursor molar ratio played a decisive role in particle stability. A 1:1 Cu:Ag ratio produced uniform particles with reduced susceptibility to surface oxidation, while Ag-rich compositions (1:3 Cu:Ag) showed increased agglomeration and partial oxidation after synthesis. Overall, this study demonstrates that careful adjustment of gas atmosphere, synthesis temperature, and precursor composition enables control over the morphology and compositional stability of Cu, Ag, and Cu–Ag powders produced by USP. These findings provide practical guidance for the scalable preparation of mono- and bimetallic metal powders for applications in electronics, catalysis, and energy-related technologies. Full article

Droplet microarrays are increasingly used for miniaturized, high-throughput biochemical assays, yet their fabrication commonly relies on complex lithographic processes, custom masks, or specialized coatings. Here we present a simple method for generating hydrophilic arrays on hydrophobic plastic substrates by combining ultrasonic atomization with off-the-shelf perforated masks. A fine mist of poly(vinyl alcohol) (PVA) solution is directed through commercial diamond sieves onto polypropylene (PP) sheets and polystyrene (PS) sheets, forming hydrophilic spots surrounded by the native hydrophobic background. Static contact angle measurements confirm a strong local contrast in wettability (from 100.85 ± 0.91° on untreated PP to 39.96 ± 0.71° on patterned spots, from 95.68 ± 3.61° on untreated PS to 52.00 ± 0.85° on patterned spots), while Image analysis shows droplet CVs of 6–8% in aqueous dye solutions for 1.2–2.0 mm masks; in complex media (LB), droplet uniformity decreases. By mounting the moving mask on a motorized stage, we generate one-dimensional reagent gradients simply by controlling the moving mask motion during atomization. We further demonstrate biological compatibility by culturing Escherichia coli in LB droplets containing resazurin, and by performing localized antibiotic screening using a moving mask-guided streptomycin gradient. The resulting droplet-wise viability data yield an on-chip dose–response curve with an IC₅₀ of 5.1 µg · mL⁻¹ (95% CI: 4.5–5.6 µg·mL⁻¹), obtained from a single array. Covering droplets with Electronic Fluorinated Fluid maintains volumes within 5% of their initial value over 24 h. Compared with conventional droplet microarray fabrication, the proposed method eliminates custom mask production and cleanroom steps, is compatible with standard plastic labware, and intrinsically supports spatial gradients. These attributes make masked ultrasonic atomization a practical platform for high-throughput microfluidic assays, especially in resource-limited settings. Full article