Atomic Force Microscopy Characterization Research Articles

Comparative Analysis of Surface Characterization Techniques for Atomic Layer Etching

The growing demand for precise atomic level control in device fabrication has led to the rising popularity of Atomic Layer Etching (ALE).1-3 As the name implies, the process facilitates layer-by-layer material removal in an atomic scale, making low surface damage one of the key features of this process. The low-power ion bombardment and the self-limited nature of different process steps help to reduce the damage induced by ALE. However, the damage is not easy to characterize. Atomic Force Microscopy (AFM) is one of the methods that is widely used for surface characterization. However, roughness measurements of the surface using AFM may be misleading as it primarily reflects the top surface, which is typically composed of native oxide rather than the actual Si surface.In this work, we discuss how we used X-Ray reflectometry (XRR) together with ellipsometry to measure the damage induced to the Si device layer of a Silicon on Insulator (SOI) wafer.The experiments were done on an SOI wafer with a 55 nm thick device layer and 145 nm box layer. In order to remove native oxide, all samples were treated with Buffered oxide etch (BOE) 10:1 right before the etch process. The cyclic process was performed in a commercial Inductively Coupled Plasma Reactive Ion Etcher (ICP-RIE) Takachi™ tool from Plasma-Therm LLC, USA. The process gases were Chlorine to activate the Si surface and Ar to remove the activated surface. There was no plasma during activation and purging, it was only ignited during the removal step. XRR, AFM, and ellipsometry characterizations were used to monitor the damage induced by the process. These methods were used to measure the surface roughness before and after the process. In the ellipsometry model, a damage layer is incorporated to evaluate the Si surface that has undergone plasma bombardment resulting in its transformation into amorphous Si. This layer is typically referred to as the surface damage layer. The XRR can measure the roughness on Si layer right beneath the native oxide which again demonstrates the surface damage. On the other hand, AFM measures the roughness at the surface of native oxide.Our results show that while in XRR and ellipsometry, the roughness change follows the same trend, the AFM measurement is not. Results have revealed that in the case of a non-ALE process, both XRR and ellipsometry techniques exhibit a substantial level of surface damage, whereas AFM indicates lower damage. This provides evidence that AFM alone may not be a reliable approach for assessing surface damage. In addition, both XRR and ellipsometry confirm a thick native oxide on top which is very much correlated to the damage. Typically, the thickness of the native oxide is in the ranges between 15-25 Å, and our results support that the thickness of the measured native oxide layer increases with the level of surface damage.

Atomic Force Microscopy Characterization of Electrochemically Polished Nickel-Titanium Memory Alloy

Atomic force microscopy (AFM) is a powerful characterization technique used for monitoring metals or metal alloys surfaces changes [1-14]. AFM works by using a small probe, typically with a sharp tip, to scan the surface of a sample. As the probe moves over the surface, it measures the height and other properties of the surface topography, allowing for detailed analysis of the surface characteristics. Using AFM, it is possible to obtain high-resolution images in 2-dimintinal (2-D) or 3-dimintinal (3-D), allowing for detailed analysis of the surface morphology, roughness, and other properties. AFM can also be used to measure surface features, such as the height and depth of surface defects, or the thickness of surface coatings.Smooth surfaces of metals or metal alloys are needed for many biomedical applications such as implants and stents. Electrochemical polishing (EP) is a process used to smooth and improve the surface finish of metals or alloys by selectively removing surface roughness using an optimum electric current. The resulting surface can have a highly polished and uniform finish. In this study, AFM is used to monitor the surface changed before and after EP of memory alloy (Nickel-Titanium, Ni-Ti Alloy). AFM image of a Ni-Ti Alloy’s surface is polished using a current density ranging from 0 to 0.147 A/cm2, which shows a highly polished surface after for 15 minutes. Surface roughness of the Ni-Ti alloy in ionic liquid as an acid free EP resulted in surface roughness significantly is reduced from 64 nm (before EP) to 11 nm without significantly altering the alloy elemental composition. This study provides an electrochemical acid free EP method to effectively control the relative smoothness of Ni-Ti implants at the nanoscale (less than 12 nm) which could offer many potential biomedical applications including controlling cell interactions with Ni-Ti alloy at bio-interfaces. Overall, AFM is a powerful tool for characterizing metal surfaces after electrochemical polishing, providing detailed information about the surface morphology and chemical composition that can be useful for a range of applications, from materials science research to quality control in manufacturing. References Mahapatro, T. D. Matos Negrón, C. Bonner, and T. M. Abdel-Fattah, J. Biomater. Tissue Eng., 3, 196-204 (2013).Bhure, A. Mahapatro, C. Bonner, T. M. Abdel-Fattah, Materials Science and Engineering: C, 33(4), 2050-2058 (2013).Bhure, T. M. Abdel-Fattah, C. Bonner, J. C. Hall, and A. Mahapatro, Applied Surface Science, 257(13), 5605-5612 (2011).M. Abdel-Fattah, D. Loftis and A.Mahapatro, Journal of Biomedical Nanotechnology, 7(6) 794-800 (2011).M. Abdel-Fattah, D. Loftis and A. Mahapatro, Journal of Surfaces and Interfaces of Materials, 3, 67-74 (2015)JD Loftis, TM Abdel-Fattah, Colloids and Surfaces A: Physicochemical and Engineering Aspects 511, 113-119 (2016)M. Abdel-Fattah, D. Loftis and A. Mahapatro, Nanoscience and Nanotechnology, 5(2), 36-44 (2015)Bhure, T. M. Abdel-Fattah, C. Bonner1, J. C. Hall, and A. Mahapatro, Journal of Biomedical Nanotechnology, 6(2), 117-128 (2010).M. Abdel-Fattah, D. Loftis, ECS Transactions, 25, (39), 57-61 (2010).M. Abdel-Fattah, D. Loftis, A. Mahapatro, ECS Transactions, 25(19), 57-61 (2010).M. Abdel-Fattah, Derek Loftis, ECS Transactions, 25(7), 327-332 (2009).AI Wixtrom, JE Buhler, CE Reece, TM Abdel-Fattah, Journal of The Electrochemical Society 160 (3), E22 (2013)AI Wixtrom, JE Buhler, CE Reece, TM Abdel-Fattah, Journal of Environmental Chemical Engineering 1 (1-2), 18-22 (2013)M. Abdel-Fattah and J, D. Loftis, Sustainable Chemistry, 3(2), 238-247 (2022)M. Abdel-Fattah and J. D. Loftis, Molecules, 25, 23, 5712 (2020)

Thermal treatment enhanced the hydrophobicity of PVDF hollow fibers membrane for brine treatment using membrane distillation

The objective of this research was to explore the impact of thermal treatment on the characteristics and performance of Poly (vinylidene fluoride) (PVDF) hollow fiber (HF) membranes utilized in direct contact membrane distillation (DCMD). To assess the effects of thermal treatment, the PVDF polymer's allotropy and crystallinity were analyzed using Fourier transform infrared ATR-FTIR and Differential scanning calorimetry (DSC). The thermal treatment predominantly affected the α-phase of the membrane, leading to increased hydrophobicity. On the other hand, Atomic Force Microscopy (AFM) characterized the membrane surface morphology. The AFM characterization revealed an increment in surface membrane roughness leading to an improvement in membrane hydrophobicity. This straightforward technique of thermal treatment resulted in improved membrane properties for DCMD application, such as increased LEP, porosity, and hydrophobicity, as well as reduced water uptake. The DCMD's efficacy was then evaluated using seawater reverse osmosis (SWRO) brine and it was observed that thermal treatment improved flux while slightly reducing salt rejection. In conclusion, these findings display the potential of thermal treatment to enhance the performance of PVDF HF membranes for DCMD applications.

Atomic force microscopy and scanning electron microscopy characterization of the controlling of surface morphology of epoxy‐amine‐cured spin‐coated films

AbstractAtomic force microscopy (AFM) was successfully used to study spin‐coated, amine‐cured epoxy film microstructure and morphology. The air‐epoxy and epoxy‐substrate interfaces were examined using tapping‐mode height and phase imaging AFM. The impact of relative humidity on the morphology and microstructure of the surfaces was determined. AFM was able to elucidate the changes on the surface as relative humidity during processing increased. It was observed that large nodular formations formed on the epoxy surface expose to the air but not epoxy surface formed on the substrate in addition to varying regions of more or less compliant structures, which was attributed to carbamate formation caused by the amine curing agent reaction with atmospheric CO2. Scanning electron microscopy (SEM) was used to further elucidate interface and interphase morphology of spin‐coated epoxies. Experimentation also demonstrated that post‐curing above the glass transition did not change the morphology structure, suggesting surface structures are “locked‐in.” SEM was used to further elucidate how the interface and interphase change with changing environmental conditions at both the air‐epoxy and epoxy‐substrate interface/interphases, including the impact of atmospheric CO2 on Marangoni cell formation.

Atomic Force Microscopy Characterization of Polyacrylamide Substrate for Traction Force Application

Atomic Force Microscopy (AFM) technology has ushered researchers to directly observe surface topology and the substrate mechanical properties using specialized probe. AFM is one of the microscopic techniques with the highest lateral resolution which can be employed in air or even in liquids. In this experiment, we characterized the local elastic properties of the polyacrylamide (PA) hydrogel using Atomic Force Microscopy (AFM). PA consists of huge units of an organic acrylamide monomers which can be saturated to form a highly water-swollen hydrogel. The hydrogel offers tunable density with a high degree of pliability which depends of its applications. Such applications of PA hydrogel can be in cell substrate studies and measurement of cell-generated forces. Our results with AFM measurement yielded force-distance curves were used to determine the elastic behaviour of the polyacrylamide (PA) hydrogel. Analysis has shown that 15% w/v PA hydrogel concentration has Young’s modulus, Yav=1608.9 ± 1.3 kPa (n=8) and transverse stiffness, Kav=88.7 ± 9.7 μN/nm (n=8) at Thus, elasticity measurements has provided useful insights for the future experiment on traction force microscopy with amoeboid organism.

Smart Molecularly Imprinted Polymer Based on Liquid Crystals for Herbicide Recognition

This study focuses on the development and characterization of molecularly imprinted thin films in the absence and presence of a liquid crystal monomer, as well as the evaluation of these materials for recognition of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). Molecular imprinted polymers (MIPs) and non-imprinted polymers (NIPs) were prepared by using two functional monomers, n-butylmethacrylate (BMA) and liquid crystalline (LC) 6-(4-cyanophenyl-4′phenoxy) hexyl acrylate (A6OCB). The resulting (MIPs) and (NIPs) materials were characterized by infrared spectroscopy (FTIR), Raman spectroscopy, polarized optical microscopy (POM), and atomic force microscopy (AFM). The entire monomer consumption, as well as the successful loading and extraction of the 2,4-D molecules, were validated by FTIR and Raman analyses. POM and AFM characterization revealed that the percentage of liquid crystal influenced the distribution of the liquid crystal domains and that the MIP films exhibited remarkable porosity. The experimental results revealed that the MIP films had a substantially higher adsorption capacity toward 2,4-D than the NIP materials and that increasing the liquid crystal content increased the adsorption capacity of both the MIP and NIP films. The selectivity tests in the presence of phenoxyacetic acid (POAc) showed that the MIP films exhibited higher affinity for 2,4-D than for the POAc.

Improving anti-fouling properties of alumina tubular microfiltration membranes through the use of hydrophilic silica nanoparticles for oil/water separation

ABSTRACT In this study, hydrophilic silica nanoparticles (Si NPs) were used to modify α-alumina tubular membranes to improve their performance in terms of flux, oil rejection, and anti-fouling properties. Our work focuses on enhancing membrane performance, particularly for difficult applications such as produced water treatment. The prepared membranes were applied for oil-in-water emulsion treatment. After coating hydrophilic Si NPs, the oil contact angle improved from 133.8° to 171.4°. To prevent Si NPs from leaching off the surface of α-alumina tubular membranes, polyvinyl alcohol was used to coat the membranes as a pre-treatment step before Si NP modification. After coating the membrane with Si NPs, the roughness of the membrane surface decreased, likely leading to less fouling. After coating Si NPs, Total Organic Carbon rejection increased from 93.1% for pristine α-alumina tubular membranes to 97.7% for silica-modified membranes because of hydrophilic improvements of the modified membranes. The Si NP coating improved the anti-fouling property of membranes with the flux recovery ratio increasing from 71.3% for pristine α-alumina tubular membranes to 85.9% for silica-modified membranes. Scanning Electron Microscopy, Energy-dispersive X-ray spectroscopy, oil contact angle, and Atomic Force Microscopy characterization tests were done. The tests showed successful Si NPs impregnation and altered wettability.

Quantification of the Stability of ALD-Grown TiO2 Protective Coatings on Photoanodes for Solar Water Splitting

Semiconducting photoabsorbers used in photoelectrochemical applications often exhibit low stability under operating conditions. One strategy implemented in recent years to prevent corrosion of photoelectrodes is the application of thin films of titanium dioxide (TiO2), coated by atomic layer deposition (ALD). However, the stability of these coatings under photoelectrochemical conditions is also limited. We are using spectroscopic ellipsometry (SE) and in-situ atomic force microscope (AFM) characterization[1, 2] in order to quantify the influence of the coating process parameters and of post-deposition treatments on the degradation of these protective layers. Here we show our recent investigations under anodic operation in acidic environment. For fully amorphous TiO2 layers, a significant contributor to the corrosion is a purely chemical process, with an activation energy of 57 kJ/mol. Furthermore, the degradation rate doubles upon illumination under simulated sunlight. With increasing pH, the stability increases significantly. Partially crystalline protective coatings exhibit improved stability under operating conditions in sulfuric acid.

Ring-Closing Reactions of Porphyrins on Noble Metal Surfaces

On-surface chemistry protocols provide elegant routes to individual molecular complexes, oligomers, and hybrid structures at confining interfaces, yielding distinct chemical, physical, and structural properties [1]. In this context, porphyrins and other tetrapyrroles represent versatile precursors that can undergo metalation, ring-opening, and ring-closing reactions. Furthermore, they are often used as functional tectons for self-assembled molecular films, metal-organic coordination networks, and covalent architectures at interfaces [2].We will report on temperature-induced ring-closing reactions of porphyrins on single crystalline Ag and Au surfaces in an ultrahigh vacuum environment. Examples covered include dehydrogenative homocoupling as well as intramolecular ring-closing. Specifically, distinct oligomers including square-type porphyrin tetramers featuring a planar, central antiaromatic cyclooctatetraene (COT) moiety were achieved on a Ag(100) support by employing unsubstituted Zn- and free-base porphines (see Figure) as precursors [3]. Low-temperature scanning tunnelling microscopy (STM), spectroscopy (STS), and bond-resolved atomic force microscopy (AFM) supported by complementary theoretical modelling were used to comprehensively characterize chemical structure and electronic properties of the square-type tetramers with sub-molecular resolution. Furthermore, the synthesis of π-extended oxygen-embedded porphyrins via O-annulation on Au(111) will be discussed. This surface chemical approach yields high selectivity and yield for planar porphyrin products with distinct symmetries and oxygen content that is not achieved by solution chemistry. The bond-resolved AFM characterization is complemented by X-ray photoelectron spectroscopy measurements. These studies thus give access, and insights, to novel porphyrinoids with distinct properties on noble metal supports.

An experimental study of triboelectrostatic particle charging behavior and its associated fundamentals

Triboelectrostatic separation is a unique dry particle separation process that has been applied to many industrial applications. However, little attention has been directed to the process of charge transfer during the particle collision and friction which is critical for the success of triboelectrostatic separation. The present study has been conducted to quantify the effects of particle size, collision speed, contact mode (collision or friction), etc. on the charge density, surface potential, morphology, etc. of quartz particles based on macroscopic triboelectrostatic charge measurements and microscopic atomic force microscopy (AFM) characterization. The macroscopic charging performance results showed that the charge to mass ratio of quartz particles depended on process parameters such as feed rate and charger rotation speed and the highest charge to mass ratio reached −56.21 μC/g. The microscopic AFM characterization data reveals that the increase in particle size and collision velocity fundamentally enhanced the triboelectrostatic charging process. The surface potential of quartz increased from −60.60 mV to −477.15 mV with increasing PVC particle size from 280 μm to 1250 μm and similar behavior was observed with increasing the collision velocity from 0.99 m/s to 2.62 m/s. The change in contact mode only changed the magnitude of charge transfer but did not change the polarity of charged particle. The process of charge transfer was accompanied with the change of surface morphology and the degree of change in surface morphology was not directly related to the amount of charge transfer.

Patterning two‐dimensional semiconductors with thermal etching

AbstractThe controllable synthesis of complicated nanostructures in advanced two‐dimensional (2D) semiconductors, such as periodic regular hole arrays, is essential and remains immature. Here, we report a green, facile, highly controlled synthetic method to efficiently pattern 2D semiconductors, such as periodic regular hexagonal‐shaped hole arrays (HHA), in 2D‐TMDs. Combining the production of artificial defect arrays through laser irradiation with anisotropic annealing etching, we created HHA with different arrangements, controlled hole sizes, and densities in bilayer WS2. Atomic force microscopy (AFM), Raman, photoluminescence (PL), and scanning transmission electron microscopy (STEM) characterization show that the 2D semiconductors have high quality with atomical clean and sharp edges as well as undamaged crystals in the unetched region. Furthermore, other nanostructures, such as nanoribbons and periodic regular triangular‐shaped 2D‐TMD arrays, can be fabricated. This kind of 2D semiconductors fabrication strategy is general and can be extended to a series of 2D materials. Density functional theory (DFT) calculations show that one WS2 molecule from the edges of the laser‐irradiated holed region exhibits a robust etching activation, making selective etching at the artificial defects and the fabrication of regular 2D semiconductors possible.image

Flexible genosensors based on polypyrrole and graphene quantum dots for PML/RARα fusion gene detection: A study of acute promyelocytic leukemia in children

Acute promyelocytic leukemia (APL) in children is associated with a favorable initial prognosis. However, minimal residual disease (MRD) follow-up remains poorly defined, and relapse cases are concerning due to their recurrent nature. Thus, we report two electrochemical flexible genosensors based on polypyrrole (PPy) and graphene quantum dots (GQDs) for label-free PML-RARα oncogene detection. Atomic force microscopy (AFM), scanning electron microscope (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were used to characterize the technological biosensor development. M7 and APLB oligonucleotide sequences were used as bioreceptors to detect oncogenic segments on chromosomes 15 and 17, respectively. AFM characterization revealed heterogeneous topographical surfaces with maximum height peaks for sensor layers when tested with positive patient samples. APLB/Genosensor exhibited a percentage change in anode peak current (ΔI) of 423 %. M7/Genosensor exhibited a ΔI of 61.44 % for more concentrated cDNA samples. The described behavior is associated with the biospecific recognition of the proposed biosensors. Limits of detection (LOD) of 0.214 pM and 0.677 pM were obtained for APLB/Genosensor and M7/Genosensor, respectively. The limits of quantification (LOQ) of 0.648 pM and 2.05 pM were estimated for APLB/Genosensor and M7/Genosensor, respectively. The genosensors showed reproducibility with a relative standard deviation of 7.12 % for APLB and 1.18 % for M7 and high repeatability (9.89 % for APLB and 1.51 % for M7). In addition, genetic tools could identify the PML-RARα oncogene in purified samples, plasmids, and clinical specimens from pediatric patients diagnosed with APL with high bioanalytical performance. Therefore, biosensors represent a valuable alternative for the clinical diagnosis of APL and monitoring of MRD with an impact on public health.

Atomic Force Microscopy Analysis of Aluminum Layer Properties and Correlation to Masking Functionality in Copper Plating Metallization for Solar Cells

The native AlOx grown on a thin sputtered aluminum layer can be used as mask for electroplating copper, e.g., for metallizing silicon heterojunction (SHJ) solar cells. Effects that influence the masking quality for selective electroplating are studied herein. Atomic force microscopy characterization in PeakForce mode highlights the presence of some insulation defects in the native AlOx due to local contamination, pinholes, or tunneling currents. A focused ion beam/scanning electron microscopy analysis is further conducted to understand some defects in detail. The AlOx insulation can be improved by adsorbing a self‐assembled monolayer, which is mainly required along the process sequence to adjust the surface wetting of the Al for optimal NaOHaq printing. The mask quality and complete metallization sequence for solar cells are demonstrated on industrial SHJ precursors. Inkjet‐ and FlexTrail‐printing of NaOHaq are shown to be suitable to pattern the Al layer. Promising conversion efficiency comparable to screen‐printing reference is reached on large area.

Extracellular Electron Transfer in Microbiologically Influenced Corrosion of 201 Stainless Steel by Shewanella algae.

The microbiologically influenced corrosion of 201 stainless steel by Shewanella algae was investigated via modulating the concentration of fumarate (electron acceptor) in the medium and constructing mutant strains induced by ΔOmcA. The ICP-MS and electrochemical tests showed that the presence of S. algae enhanced the degradation of the passive film; the lack of an electron acceptor further aggravated the effect and mainly affected the early stage of MIC. The electrochemical tests and atomic force microscopy characterization revealed that the ability of ΔOmcA to transfer electrons to the passive film was significantly reduced in the absence of the c-type cytochrome OmcA related to EET progress, leading to the lower corrosion rate of the steel.

Growth evolution and polarization-dependent photoluminescence of lateral InSb/CdTe nanowires

The evolution of lateral InSb nanowires (NW) grown on CdTe (001) substrate by increasing of the InSb thickness is reported. At 10-nm growth of InSb, NW with narrow lateral width of ∼ 70 nm and high NW density (∼18 μm−1) are obtained. The evolutional description of InSb NW growth based on the atomic force microscopic characterization is presented. The intrinsic strain at the interface and top InSb layer is revealed by x-ray diffraction analysis. The strong polarization-dependent photoluminescence (PL) of NW is observed. The polarization degree of NW is ∼ 80% and 56% when the excited laser and the emission PL are polarized, respectively. The latter can be attributed to the shape anisotropy.

Synthesis and characterization of a large-quantity of functionalized graphene from graphite by a facile bubble-exfoliation method

In this work, functionalized graphene (FG) was synthesized based on an improved bubble-exfoliation method from cheap defective graphite. By using the improved method, we synthesized a significant amount of FG in a short time while maintaining the acid usage at a low level compared to previous works. Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and ultraviolet–visible spectroscopy (UV–Vis) techniques validated the oxidation effect of the synthesis process on FG, which is in line with the addition of functional groups to it. Transmission electron microscopy, atomic force microscopy, Raman and XRD characterizations showed that FG mainly consists of a thin few-layer structure. X-ray photoelectron spectroscopy (XPS) analysis was also in agreement with the chemical structure validated by FTIR, Raman and UV–Vis, indicating that the functional groups of FG are primarily hydroxyls. Furthermore, it was revealed that the presence of pentagonal–heptagonal defects, confirmed by XPS results, in the graphite source have a significant impact on the success of the synthesis route as the defects play the role of activators for persulfate in the oxidation process.

Modulating the Mechanical Resonance of Huh-7 Cells Based on Elasticity of Adhesion Proteins.

The atomic force microscope (AFM) has been used in cell biology for a decade. AFM is a unique tool for investigating the viscoelastic characteristics of live cells in culture and mapping the spatial distribution of mechanical properties, giving an indirect signal of the underlying cytoskeleton and cell organelles. Although several experimental and numerical studies were conducted to analyze the mechanical properties of the cells. We established the non-invasive Position Sensing Device (PSD) technique to evaluate the resonance behavior of the Huh-7 cells. This technique results in the natural frequency of the cells. Obtained experimental frequencies were compared with the numerical AFM modeling. Most of the numerical analysis were based on the assumed shape and geometry. In this study, we propose a new method for numerical AFM characterization of Huh-7 cells to estimate its mechanical behavior. We capture the actual image and geometry of the trypsinized Huh-7 cells. These real images are then used for numerical modeling. The natural frequency of the cells was evaluated and found to be in the range of 24 kHz. Furthermore, the impact of focal adhesion (FA's) stiffness on the fundamental frequency of the Huh-7 cells was investigated. There has been a 6.5 times increase in the natural frequency of the Huh-7 cells on increasing the FA's stiffness from 5 pN/nm to 500 pN/nm. This indicates that the mechanical behavior of FA's leads to change the resonance behavior of the Huh-7 cell. Hence FA's are the key element in controlling the dynamics of the cell. These measurements can enhance our understanding of normal and pathological cell mechanics and potentially improve disease etiology, diagnosis, and therapy choices. The proposed technique and numerical approach are further useful in selecting the target therapies parameters (frequency) and evaluating of mechanical properties of the cells.

Design and fabrication of energetic Al/Ni exploding foil with enhanced energy efficiency and plasma density for direct ignition

In order to lower the firing voltage, an energetic Al/Ni exploding foil (Al/Ni-EF) with enhanced energy efficiency and plasma density was prepared in this study, to realize the direct ignition of pyrotechnics. An Al/Ni reactive multilayer foil (Al/Ni-RMF) was firstly synthesized by magnetron sputtering and wet etch method, and its structure and exothermic behavior were investigated. Scanning Electron Microscopy, Atomic Force Microscope and X-ray Diffraction characterizations confirmed the periodic layer structure of Al/Ni-RMF with a total thickness of 4 μm. The highest heat release in Al/Ni-RMF could be achieved theoretically when the ratio of Al and Ni was 1.5, and thus the thickness of single Al and Ni layer was determined to be 300 nm and 200 nm, respectively. The obtained Al/Ni-RMF was subsequently fabricated to be an exploding foil, and its electric explosion performance was further studied. Energy efficiency of the Al/Ni-EF was measured to be 85.9% during the electric explosion process, which was 30.9% higher than that of Cu exploding foil (Cu-EF). The plasma generated at Al/Ni-EF had larger volume, longer duration time and higher temperature than Cu-EF due to the intermetallic reaction between Al and Ni, which was beneficial for the direct ignition of Boron/Potassium Nitrate composition (B/KNO3, BPN). Afterwards, a special Al/Ni-EF ignitor without slapper was constructed, and the fierce ignition of BPN at the minimum discharge voltage of 800 V was observed. Above results confirmed the feasibility of direct ignition, such a unique strategy was beneficial for the development of low-energy, low-cost and miniaturized ignitor.

Enhancing the Mechanical Properties of Corn Starch Films for Sustainable Food Packaging by Optimizing Enzymatic Hydrolysis.

The objective of this study was to investigate the effects of enzymatic hydrolysis using α-amylase from Bacillus amyloliquefaciens on the mechanical properties of starch-based films. The process parameters of enzymatic hydrolysis and the degree of hydrolysis (DH) were optimized using a Box-Behnken design (BBD) and response surface methodology (RSM). The mechanical properties of the resulting hydrolyzed corn starch films (tensile strain at break, tensile stress at break, and Young's modulus) were evaluated. The results showed that the optimum DH for hydrolyzed corn starch films to achieve improved mechanical properties of the film-forming solutions was achieved at a corn starch to water ratio of 1:2.8, an enzyme to substrate ratio of 357 U/g, and an incubation temperature of 48 °C. Under the optimized conditions, the hydrolyzed corn starch film had a higher water absorption index of 2.32 ± 0.112% compared to the native corn starch film (control) of 0.81 ± 0.352%. The hydrolyzed corn starch films were more transparent than the control sample, with a light transmission of 78.5 ± 0.121% per mm. Fourier-transformed infrared spectroscopy (FTIR) analysis showed that the enzymatically hydrolyzed corn starch films had a more compact and solid structure in terms of molecular bonds, and the contact angle was also higher, at 79.21 ± 0.171° for this sample. The control sample had a higher melting point than the hydrolyzed corn starch film, as indicated by the significant difference in the temperature of the first endothermic event between the two films. The atomic force microscopy (AFM) characterization of the hydrolyzed corn starch film showed intermediate surface roughness. A comparison of the data from the two samples showed that the hydrolyzed corn starch film had better mechanical properties than the control sample, with a greater change in the storage modulus over a wider temperature range and higher values for the loss modulus and tan delta, indicating that the hydrolyzed corn starch film had better energy dissipation properties, as shown by thermal analysis. The improved mechanical properties of the resulting film of hydrolyzed corn starch were attributed to the enzymatic hydrolysis process, which breaks the starch molecules into smaller units, resulting in increased chain flexibility, improved film-forming ability, and stronger intermolecular bonds.

Comparative study on boundary lubrication of Ti3C2Tx MXene and graphene oxide in water

The emerging use of two-dimensional (2D) nanomaterials as boundary lubricants in water offers numerous benefits over oil-based lubricants; whereas the friction reduction varies significantly with nanomaterial type, size, loading, morphology, etc. Graphene oxide (GO) and Ti3C2Tx MXene, a relatively new 2D material, are investigated as boundary lubricants in water in this study. The contact pair mainly includes Si3N4 balls and Si wafer. The results found (1) monodispersed GO offers better lubricity than monodispersed MXene under identical concentration and testing conditions; and (2) the mixed dispersion of GO and MXene (0.1 mg/ml: 0.1 mg/ml) produced the lowest friction coefficient of ∼ 0.021, a value 4× and 10× lower than that produced by comparable mono-dispersions of GO or MXene, respectively. Wear track analysis, focused ion beam microscopy, in-situ contact observation, and atomic force microscopy (AFM) characterization suggest (1) GO nanoflakes have higher adhesion than MXene and are more easily adsorbed on the tribopairs’ surfaces, and (2) GO/MXene tribofilm has a layered nanostructure constituting GO, MXene, amorphous carbon, and TiO2. We further hypothesized that the high lubricity of GO/MXene results from the synergy of GO’s high adhesiveness, MXene’s load support ability, and the low shear strength of both constituents. The present study highlights the key role of tribofilm stability in water-based boundary lubrication using state-of-the-art 2D nanomaterials.