Removal Of Surface Contaminants Research Articles

Analysis of silver metal with a Thermo Scientific K-Alpha XPS instrument at 50 and 200 eV pass energies

Silver metal was analyzed by x-ray photoelectron spectroscopy using a Thermo Scientific K-Alpha instrument with an Al Kα x-ray source (1486.6 eV). The silver survey spectrum and high-resolution Ag 3d, Ag M4N45N45, Ag M5N45N45, Ag 3p, O 1s, C 1s, Ar 2p, Ag 4p, and Ag 4s narrow scans were obtained. The sample analyzed is the standard instrument calibration silver foil mounted inside the analysis chamber of the K-Alpha. Sputtering with monoatomic Ar+ was performed prior to analysis to remove surface contamination. Narrow and survey scans were collected at 50 and 200 eV pass energy, respectively.

Wet-Chemical Synthesis of a Protective Coating on NCM111 Cathode: The Quantified Effects of Washing, Sintering and Coating

LiNixCoyMn1-x-yO2 (NCM) cathodes, especially with high Ni content, are widely expected to keep advancing the energy density of Li-ion batteries. However, ensuring a good cycle life remains a key challenge. Applying inert protective coatings on the surface of NCMs is a common route for mitigating surface-based degradation. In this study a sustainable ethanol-based wet-chemical coating method for covering the material with Al2O3 is developed and demonstrated on NCM111. The effect of the synthesis procedure is carefully evaluated to distinguish the benefits of the protective coating from the contributions of re-sintering and removal of surface contaminants, all taking place during the synthesis of the coated material. We show that while the cycling stability is significantly improved by the material regeneration alone (65% vs 79% state-of-health after 500 charge-discharge cycles at voltage range 2.7–4.3 V vs Li/Li+), the Al2O3-coated material displays further cycle life gains, maintaining 88% of initial capacity after 500 charge-discharge cycles. This work thus demonstrates both a sustainable wet-chemical coating method and the importance of establishing a proper baseline for characterization of inert protective coatings in general. The importance of both gains further prominence with the transition to inherently less stable higher Ni content NCMs.

Assessment of Surface Sterilisation Approaches for the Removal of Pollen DNA from Philaenus spumarius.

Dietary analysis of herbivorous insects relies on successfully eliminating surface contamination. If this cannot be performed reliably, then it will not be possible to differentiate between plants that the insect is feeding on and plants the insect has been in contact with, either directly or via pollen. Methods in the literature often use bleach and alcohol washes to remove contamination. We perform a controlled metabarcoding baseline study on a herbivorous, xylem-feeding insect, the Meadow Spittlebug (Philaenus spumarius), using Oxford Nanopore Technologies (ONT) sequencing, and identify possible contamination that persists after washes. Despite the reported success of methods in the literature, we find that contamination is still present, leading to possible false-positive results. We hypothesise that pollen is the main source of contamination, its robust nature making it difficult to remove, and conduct a further three experiments with the goal of removing pollen from the surface of Philaenus spumarius. This study investigates the effectiveness of robust bleach/Tween/alcohol washes, sterile gut excision (including combined with Distel application), and ultraviolet light as alternative sterilisation approaches. Overall, our findings indicate that we are unable to remove surface contamination and still detect signals that may originate in the gut. In no experiment did we unequivocally detect plant DNA that originated in the P. spumarius gut.

Achieving High Substitutional Incorporation in Mn-Doped Graphene.

Despite its broad potential applications, substitution of carbon by transition metal atoms in graphene has so far been explored only to a limited extent. We report the realization of substitutional Mn doping of graphene to a record high atomic concentration of 0.5%, which was achieved using ultralow-energy ion implantation. By correlating the experimental data with the results of ab initio Born-Oppenheimer molecular dynamics calculations, we infer that direct substitution is the dominant mechanism of impurity incorporation. Thermal annealing in ultrahigh vacuum provides efficient removal of surface contaminants and additional implantation-induced disorder, resulting in Mn-doped graphene that, aside from the substitutional Mn impurities, is essentially as clean and defect-free as the as-grown layer. We further show that the Dirac character of graphene is preserved upon substitutional Mn doping, even in this high concentration regime, making this system ideal for studying the interaction between Dirac conduction electrons and localized magnetic moments. More generally, these results show that ultralow energy ion implantation can be used for controlled functionalization of graphene with substitutional transition-metal atoms, of relevance for a wide range of applications, from magnetism and spintronics to single-atom catalysis.

Micropatterned Hydrogel‐Elastomer Hybrids for Flexible Wet‐Style Superhydrophobic Antifogging Tapes

AbstractTransparent materials widely used in applications such as eyewear, solar cells, and optical devices, often suffer from environmental challenges including fogging, surface contamination, and mechanical deformation. However, a universal strategy that resolves all these issues in a single platform remains to be resolved. Herein, a monolithic micropillar structure based on polydimethylsiloxane (PDMS) elastomer is prepared followed by subsequent assembly of hydrogel micropatterns in between the micropillar array using inkjet printing to achieve flexible wet‐style superhydrophobic antifogging tapes that are applicable to various transparent materials and curvatures. The monolithic micropillar structure with low‐surface‐energy characteristics facilitates easy removal of surface contaminants by rinsing with water while granting mechanical durability. In addition, micropatterning of hydrogels via inkjet printing not only enables to maintain optical transparency in a fogging environment but also makes the fabrication procedure more scalable. Furthermore, the strong adhesion between the hydrogel and the elastomer is shown to provide enhanced stability under repeated stretching cycles and long‐term exposure to water while the presence of a loosely cross‐linked PDMS at the bottom of the tape made it applicable to a wide range of transparent substrates without using additional adhesives.

Using sputtering parameters to mitigate argon ion sputtering induced reduction of nickel in XPS

Argon ion sputtering for depth profiling in XPS results in the preferential sputtering of oxygen in certain oxide systems. Preferential oxygen removal results in the chemical reduction of the associated cation which is observed in spectra collected following sputtering. Characterizing the effects of different sputtering parameters and developing methods to account for and to minimize changes to chemical states during sputtering would allow for greater confidence in the qualitative and quantitative analysis of the chemical states observed after sputtering. In this study argon ion sputtering was performed with monatomic and clustered argon ions on thermally oxidized NiO. Parameters for monatomic and cluster sputtering were varied to observe their effects on the induced reduction. Results show that extensive reduction is experienced for monatomic sputtering irrespective of the energy and current chosen. For cluster argon ion sputtering, reduction was mitigated when selecting either large cluster sizes or low cluster energies. Sputtering for long periods of time with low energy clusters was observed to result in the removal of surface contaminants without concomitant reduction of the nickel oxide.

Study on Nanomaterials Coated Natural Coir Fibers as Crack Arrestor in Cement Composite

The process of inclusion of carbon nanotubes as fibers in cement paste has been proved to have optimistic effect as it enhances the tensile property of cement paste composite. Coir fibers have exceptional mechanical qualities and are thus employed as reinforcement in cement composites. Epoxy resin, which has a high Young’s modulus, is an ideal component for bonding carbon nanotubes (CNTs) to coir fiber. This paper describes a novel kind of nanocomposite made of L-12 epoxy resin and CNTs at the nanolevel, along with coir fibers at the microlevel which operate as crack arrestors. To remove surface contaminants, coir fibers are first treated with sodium hydroxide (NaOH). Epoxy/CNTs polymer coatings were developed at varying CNTs fractions (0.05, 0.1, 0.15, and 0.2 wt.% of cement). Multiwalled CNTs were combined in distilled water, followed by epoxy resin and hardener (9 : 1 v/v) polymer in an ultrasonic sonicator for 90 min to ensure full dispersion of CNTs within the epoxy polymer. This blend is now coated on the treated clustered coir fiber (length 10 cm, 10 strands) and reinforced along the length of a cement composite beam 20 mm × 20 mm × 80 mm in size. Tensile and three-point tests were performed to evaluate the mechanical characteristics of the hybrid composite. The linear elastic finite element analysis is employed to distinguish their failure phenomena via fatigue or fracture behavior. The microstructure behavior and the effect of coating material on the coir fibers were investigated using scanning electron microscope and EDX analysis. The reinforcing impact of nanopolymer coated coir fiber in cement composite diminished the tensile and flexural strength after 0.1 wt.% of CNT fraction but increased the composite’s durability and Young’s modulus. Fourier transform infrared spectroscopy analysis was carried out to assess the chemical interaction between the epoxy/CNTs and the coir fibers. The simulation was performed using ANSYS workbench, and the modeling results were within an acceptable 10% range of the experimental data. Nevertheless, it can be concluded that the hybrid composite is capable of enhancing the composite’s stress and strain capacity by regulating the fracture propagation process at the crack’s end.

Effect of High-Power Laser Cleaning for Surface Contaminants Removal on SS304L

In this study, artificially formed corrosion and paint layers on 304L stainless steel (SS304L) specimen were removed using a kilowatt level high-power Nd:YAG laser. A laser power of 1140 W and a pulse duration of 89 ns were used for the corrosion removal, and a laser power of 850 W and a pulse duration of 54 ns were adopted for the paint removal. Surface composition was analyzed via electron probe micro-analysis (EPMA) and x-ray diffraction (XRD) analysis before and after the laser cleaning process, confirming that the corrosion and paint layers were successfully removed from the SS304L surface by the laser cleaning process. The effect of the laser cleaning process on the mechanical properties of SS304L was investigated. The hardness and tensile strength of the laser-cleaned specimens were analyzed to determine their mechanical properties. After the laser cleaning process, the surface hardness was slightly increased up to depths of 250 µm for the corrosion removal and up to 50 µm for the paint removal. However, only marginal changes in tensile strength and elongation were detected after the laser cleaning process. These results confirmed that laser cleaning can effectively remove surface contaminants (i.e., corrosion and paint) on SS304L with only a minimum modification of microstructure and mechanical properties.

Direct wetting of Li7La3Zr2O12 electrolyte with molten Li anode and its application in solid-state lithium batteries

Garnet Li6.5La3Zr1.5Ta0.5O12 (LLZTO) is a promising solid electrolyte for solid-state batteries (SSBs) owing to its high ionic conductivity and high chemical/electrochemical stability. However, the solid-to-solid interface between LLZTO electrolyte and Li anode restricts its application. In this work, an in-situ integration of LLZTO electrolyte with Li anode is proposed to solve this problem. Superior to reported works, the LLZTO obtained by our self-consolidation method can be directly wetted by molten Li without any surface treatment. The self-consolidated LLZTO exhibits a dense microstructure consisting of grains and interstitial phases among them, both of which are accessible to molten Li. Removal of surface contaminants on molten Li rather than that on LLZTO is a prerequisite for direct wetting. Benefiting from direct wetting, an intimate interfacial contact between the LLZTO and Li anode is achieved and the interfacial resistance is significantly reduced. The Li symmetric cell exerts a stable Li plating/stripping cycle for 1000 h at 0.20 mA cm−2 and the solid-state battery paired with LiCoO2 cathode exhibits a capacity retention of 90.0 % at 0.2 C after 200 cycles at room temperature. This work highlights the surface chemistry of electrolyte and electrode, which is crucial for designing their integration and application.

Magnetically treated water for removal of surface contamination by Malathion on Chinese Kale (Brassica oleracea L.).

Malathion® is a persistent organophosphate pesticide used against biting and chewing insects on vegetables. It is a difficult-to-remove surface contaminant of vegetables and contaminates surface and ground water and soils. Malathion® is only partially water soluble, but use of detergent carriers makes adhering Malathion® residues difficult to subsequently remove. Magnetically treated water (MTW) successfully removed Malathion® from Chinese Kale (Brassica oleracea L.), meeting Maximum Residue Load (MRL) standards. Samples were soaked in MTW for 30 min prior to detection with GC/MS/MS, 98.5±3.02% of Malathion® was removed after washing by MTW. Removal by simple washing was only ≈42±1.2% which was not nearly sufficient to meet MRL criteria.

Enhancing minority carrier lifetime in Ge: Insights from HF and HCl cleaning procedures

Efficiently passivating germanium (Ge) surfaces is crucial to reduce the unwanted recombination current in high-performance devices. Chemical surface cleaning is critical to remove surface contaminants and Ge oxides, ensuring effective surface passivation after dielectric deposition. However, Ge oxides can rapidly regrow upon air exposure. To understand the surface evolution after wet cleaning, we present a comprehensive study comparing HF and HCl deoxidation steps on p-type Ge surfaces and monitor the surface as a function of air exposure time. Distinct oxide regrowth dynamics are observed: HF-treated samples exhibit swift regrowth of all Ge oxide states, whereas HCl-treated Ge surfaces exhibit a lower concentration of low degrees of oxidation and slower or no regrowth of high oxide states even after 110 min of air exposure. In addition, the presence of Ge–Cl bonds induces different oxidation dynamics compared to the Ge–OH bonds resulting from HF cleaning. This leads to varying surface electronic band structures, with HF-treated Ge exhibiting a strong positive band bending (+0.20 eV). Conversely, HCl-treated samples display a lower band curvature (+0.07 eV), mostly due to the presence of Ge–Cl bonds on the Ge surface. During air exposure, the increased GeOx coverage significantly reduces the band bending after HF, while a constant band bending is observed after HCl. Finally, these factors induce a reduction in the surface recombination velocity after wet etching. Combining both chemical and field-induced passivation, HF-treated Ge without rinsing exceeds 800 μs.

Bleach Cleaning of Commercially Available Gold Nanopillar Arrays for Surface-Enhanced Raman Spectroscopy (SERS).

Surface-enhanced Raman spectroscopy (SERS) is a highly sensitive technique that can assist in trace analysis for biomedical, diagnostic, and environmental applications. However, a major limitation of SERS is surface contamination of the substrates used, which can complicate the spectral reproducibility, limits of detection, and detection of unknown analytes. This is especially prevalent with commercially available substrates as shipping under a controlled and clean environment is difficult. Here we report a method using dilute bleach solutions to remove surface contamination from commercially available substrates consisting of gold-coated nanopillar arrays that maintains functionality. The results show that this method can be used to remove background signals associated with typical surface contamination in commercially available substrates as well as remove thiolated self-assembled monolayers (SAMs). Results indicate the bleach oxidizes the surface contaminants, which can then be easily washed away. Although the metallic surface also becomes oxidized in this process, the surface can be reduced without loss of SERS activity. The SERS intensity of SAMs improved following bleach treatment across all concentrations studied.

Atmospheric pressure plasma application on the adhesive bonding improvement of CFRP via surface configuration comparison

AbstractCarbon fiber reinforced polymer (CFRP) has a wide range of applications in aerospace, automobile, marine, and other industries, due to its remarkable mechanical properties and lightweight. It can enhance the performance of the structural components and has been presented to be a good alternative over conventional materials. Adhesive bonding has been widely employed, and research studies on the surface modification of CFRP have been conducted to improve the load resistance of adhesive bonding, of which atmospheric pressure (AP) plasma is the most preferred method. However, there is still a lack of study on the effectiveness and strategies of AP plasma surface modification. To gain more insight, possible sources that would have influence on the adhesive bonding were analyzed by preparation of different surface configurations of CFRP. It is confirmed that AP plasma can increase the surface polarity and wettability of the carbon fiber surface. It can contribute to the removal of surface contamination element as well. Although the surface morphology and surface roughness before and after the AP plasma treatment does not show noticeable changes, the single‐lap shear strength of the contaminated samples can be effectively improved. This study validates that AP plasma is effective on surface contamination removal and bonding quality improvement, which provides a potential alternative for the adhesive bonding improvement and surface modification of carbon fiber.Highlights Surface polarity and wettability increase of CFRP by AP plasma. Surface contamination removal and bonding quality improvement by AP plasma. AP plasma provides a potential alternative method for adhesive bonding pre‐treatment. AP plasma surface modification mechanism analysis via surface characterization.

Glacial secrets uncovered: Revealing the modes of survival of metabolically active microbial communities entrapped in polar glacial ice

Glacial secrets uncovered: Revealing the modes of survival of metabolically active microbial communities entrapped in polar glacial ice

Laser Light as an Emerging Method for Sustainable Food Processing, Packaging, and Testing.

In this review article, we systematically investigated the diverse applications of laser technology within the sphere of food processing, encompassing techniques such as laser ablation, microbial inactivation, state-of-the-art food packaging, and non-destructive testing. With a detailed exploration, we assess the utility of laser ablation for the removal of surface contaminants from foodstuffs, while also noting the potential financial and safety implications of its implementation on an industrial scale. Microbial inactivation by laser shows promise for reducing the microbial load on food surfaces, although concerns have been raised about potential damage to the physio-characteristics of some fruits. Laser-based packaging techniques, such as laser perforation and laser transmission welding, offer eco-friendly alternatives to traditional packaging methods and can extend the shelf life of perishable goods. Despite the limitations, laser technology shows great promise in the food industry and has the potential to revolutionize food processing, packaging, and testing. Future research needs to focus on optimizing laser equipment, addressing limitations, and developing mathematical models to enhance the technology's uses.

Synthesis and comprehensive synchrotron-based structural analysis of Si-doped nanodiamond composite films deposited on cemented carbide

Si-doped nanodiamond composite (NDC) films were deposited on unheated WC − Co substrates by coaxial arc plasma deposition for advanced cutting tools applications. The nanoindentation test revealed changes in films hardness and Young's modulus attributed to various Si doping concentrations (0, 1, 5, and 20 at.%) and the catalytic effects of Co diffused from the substrate surface into the films. To reveal the physical origin behind these changes, the films' structure was examined by synchrotron-based Auger electron spectroscopy (AES), soft X-ray photoemission spectroscopy (XPS), and near edge X-ray absorption fine structure spectroscopy (NEXAFS). The AES and XPS analysis showed a consistent correlation between nanoindentation measurements and the estimated C sp3 fraction in the films. The NEXAFS spectra revealed intense C − C σ* resonance, consistent with the measured film hardness. The 1 at.% Si-doped film, deposited with an undoped NDC buffer layer to mitigate the Co catalytic effects, exhibited the highest hardness of 60 GPa, the largest C sp3 fraction, and the most intense CC σ* peak. Si doping resulted in the formation of C − Si sp3 bonds at the expense of C sp2 bonds, increasing the fraction of C sp3 bonds and enhancing film hardness. The synchrotron-based analysis effectively revealed the electronic states of NDC hard coatings, particularly after the removal of surface contaminants through mechanical polishing.

Laser cleaning process of high-pressure turbine blade: Characterization and removal of surface contaminants

Laser cleaning has been introduced as an effective method for removing contaminants from the surface of a turbine blade. In this investigation, a continuous wave fiber laser with a power density of 7.96 × 106 W/cm2, a wavelength of 1064 nm, and a focusing distance of 305 mm under an argon gas was applied. The used laser removed CaO-MgO-Al2O3-SiO2 (CMAS) as contaminants from the Y2O3-stabilized ZrO2 layer of a thermal barrier coating (TBC) on a high-pressure turbine blade made of a nickel-based superalloy substrate. At first, the characterization of the CMAS and TBC properties, such as thickness, roughness, and morphology, as well as phase identifications were performed. CMAS on the high-pressure turbine blade (HPTB) surface had a mixture of granular and plate structures. The major imperfections of the surface of the out-of-service HPTB were infiltration of CMAS into the TBC, chemical interaction between CMAS and the TBC, transverse cracks, delamination of the TBC, structural changes of the TBC, separation of YSZ from TGO, and deformation of the TBC on the pressure side and the leading edge of HPTB. The main aim of this work was to remove non-infiltrated CMAS from the TBC coating through the laser cleaning process. Then, various parameters of the laser cleaning process such as power and scanning speed were investigated. After that, various analyses of laser-cleaned samples such as scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), optical microscopy (OM), X-ray diffraction (XRD), thickness test, and roughness measurement were accomplished for the optimum parameters of the laser cleaning process. Finally, the mechanism involved in the laser cleaning process to remove the contamination was presented in detail. The results demonstrated that the optimum parameters of the laser cleaning process to completely eliminate targeted contaminants were a power density of 7.16 × 106 W/cm2, a scanning speed of 0.01 mm/s, and a focusing distance of 305 mm under an argon gas atmosphere.

A novel application of acrylic resin UV-Curing methodology for radioactive surface decontamination

A unique UV-Curing method is provided for decontamination of radioisotopes on the surfaces which has radiation dealing facilities. In this method acrylic UV-Curing resin was poured on a contaminated simulated surface followed by UV irradiation. The resin interacted with the contaminated surface and after polymerization, the solidified resin was then stripped off, leaving behind a clean surface. The present study is the proof-of-concept of a novel application of acrylic resin UV-Curing methodology for Radioactive surface contamination removal to create a economical clean, effective and safe environment with minimal waste generation post processing ready for environment friendly incineration.

Reversing the Chemical and Structural Changes of Prussian White After Exposure to Humidity to Enable Aqueous Electrode Processing for Sodium-ion Batteries

Prussian White is a promising active material for the positive electrode of sodium-ion batteries as it is comprised of Na, Mn, Fe, C, and N and thus offers high sustainability and low cost. However, exposure of Prussian White to moisture results in chemical changes due to the formation of surface contaminants, as well as structural changes due to the absorption of water into the bulk crystal structure. Here we report an analysis of the formation rate of surface contaminants and bulk water absorption by weight tracking, infrared spectroscopy, and X-ray diffraction over extended periods of storage in high relative humidity air for fully sodiated Na1.8Mn0.8Fe0.2[Fe(CN)6]0.9 and partially sodiated Na1.3Mn0.8Fe0.2[Fe(CN)6]0.9. Fully sodiated Prussian White gains almost 20% in mass due to the formation of interstitial water during 20 h of storage in 100% relative humidity at 25 °C. Surface hydroxides and carbonates are found after storage and a structural change from the rhombohedral to a monoclinic crystal structure is observed. It is found that vacuum drying of Prussian White powder or electrodes at 150 °C can remove the majority of interstitial water and restore the rhombohedral crystal structure, but not remove surface contaminants. Prussian White immersed in water during aqueous electrode processing also shows interstitial water and a monoclinic crystal structure, but no surface contaminants. This suggests that aqueous electrode processing of Prussian White is feasible when effective drying strategies are employed. Indeed, Prussian White electrodes made from H2O-based slurries with CMC/NaPAA binder vacuum-dried at 150 °C show higher specific capacity and similar capacity retention in full cells as Prussian White electrode made from NMP-based slurries with PVDF binder.

Enhancement of temperature-modulated NbO2-based relaxation oscillator via interfacial and bulk treatments

This work demonstrates oscillation frequency modulation in a NbO2-based relaxation oscillator device, in which the oscillation frequency increases with operating temperature and source voltage, and decreases with load resistance. An annealing-induced oxygen diffusion at 373 K was carried out to optimize the stoichiometry of the bulk NbO2 to achieve consistent oscillation frequency shift with device temperature. The device exhibits stable self-sustained oscillation in which the frequency can be modulated between 2 and 33 MHz, and a wider operating voltage range can be obtained. An additional surface treatment step was employed during fabrication to reduce the surface roughness of the bottom electrode and to remove surface contaminants that affect the interfacial properties of the device. The device frequency tunability coupled with high oscillating frequency and high endurance capability of more than 1.5 × 108 cycles indicates that the Pt/NbO2/Pt device is particularly suitable for applications in an oscillatory neural network.