Sample Topography Research Articles

QEMSCAN® automated mineralogical analysis of PM2.5 and PM4: A preliminary study of underground coal mine dust from Poland and Slovenia

Determining the physical and chemical properties of airborne dusts in occupational settings is essential for assessing their potential toxicity as well as the effectiveness of respiratory protective equipment and dust mitigation measures. Here, we report the first successful QEMSCAN® automated mineralogical analysis of potentially toxic PM4 and PM2.5 dust from deep coal mines in Poland and Slovenia. QEMSCAN® was setup to automatically delimit 100,000 ‘particles’ per sample, based on average atomic number contrast, subject these to X-ray elemental analysis at points in a grid pattern (0.5 µm spacing), assign a mineral name to each point and then output the results as particle size, shape, mineralogy and mineral associations data and as mineral maps. The dusts were prepared as dispersions on a polyethylene sheet so that coal particles, with a slightly higher BSE signal, could be recognized from their substrate. Samples were analyzed repeatedly and in different orientations to determine the effects of sample geometry and topography. QEMSCAN® mineral identifications were manually checked using standard SEM X-ray elemental analysis. From a pilot study of Polish and Slovenian coal dust samples, PM4 and PM2.5 contain varying proportions of coal, quartz and other silicates, sulphides, sulphates, carbonates, oxides and other minerals, and notable concentrations of fly-ash particles. That some of these components may be toxic when inhaled, particularly the quartz and fly-ash, highlights the need for larger scale and wider ranging studies. The further potential of the newly developed QEMSCAN® methodology is discussed.

Influence of heating temperature on the optical response properties and surface relief patterns of TiO2/GeO2/ormosils composite films containing azobenzene

With the progress of modern integrated optical technology, organic-inorganic composite materials have been widely used in integrated optoelectronic devices. Because of satisfying optical response properties among azobenzene, it will be an ideal choice to introduce the material into organic-inorganic composite materials. TiO2/GeO2/ormosils composite films containing azobenzene were prepared by combining the solgel technique with the spin-coating process. The optical transmission modes and loss of as-prepared samples at different transmission wavelengths were researched by a prism coupler. The result shows that the composite film is multi-mode transmission at the transmission wavelength of 633 nm and single-mode transmission at 1538 nm. The transmission loss is sufficient for applications in optical elements. The response properties and Fourier transform infrared spectroscopy of as-prepared samples at different heating temperatures were also studied. The composite films obtained at 50°C have the best optical response properties. Furthermore, the banding energy and chemical composition among the films were measured through x-ray photoelectron spectroscopy. Finally, the surface topography of as-prepared samples was observed by atomic force microscopy. The surface of the composite film appears with patterns of relief under the appropriate temperature. The above results show that the as-prepared TiO2/GeO2/ormosils composite films containing azobenzene will be a kind of ideal material in the field of integrated optics applications.

Analysis of PI-Control for Atomic Force Microscopy in Contact Mode

This article investigates the properties, from a nonlinear control system standpoint, of atomic force microscope (AFM) systems, whenever operated in contact mode and controlled in the vertical direction by proportional-integral control law. By modeling the AFM as a system in which a piezo-electric actuator and a cantilever mutually interact in order to produce the sample topography, ensuing distortions affecting the quality of the yielded topography measurement are naturally cast and analyzed. The proposed investigation considers distortions due to the inception of hysteresis and vibrational dynamics within the piezo-actuator or provoked by system saturation. Both hysteresis and saturation are inherently nonlinear phenomena and are modeled as such. In spite of the inherently nonlinear nature of the AFM dynamics, investigations of the contact mode case from a nonlinear standpoint are lacking within the AFM literature. As the topography yielded by the AFM completely relies on its control algorithm, to the point that the measurement itself <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">corresponds</i> to the control action <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$v(t)$ </tex-math></inline-formula> , it becomes of paramount importance to understand how <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$v(t)$ </tex-math></inline-formula> relates to the actual topography, and how such a relationship is affected by the aforementioned distortions. This article hence intends to contribute to the AFM literature, by providing a study in which the very meaning of the image measurement yielded by the AFM is investigated, in the light of distortions due to nonlinear phenomena. The AFM is considered to be operated in contact mode with a PI algorithm. Furthermore, as a byproduct of the derived nonlinear stability analysis, a novel, model-based algorithm for tuning the PI control gains is provided. Finally, experimental results are presented and analyzed in view of the derived theory.

Research on the Performance of Composite Cantilever Beam under Special Environmental Condition

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;This paper will focus on the root facture problem of carbon fibre reinforced polymers (CFRP) material of aircraft winglets through ABAQUS simulation analysis regarding the aircraft takeoff and landing from high altitude at the constant and low-temperature experimental analysis and topography analysis. The innovative purpose of this paper is to identify the critical failure stress of the cantilever bending of unidirectional and orthogonal, embedding carbon nanotube reinforcement, and exploring the embedded carbon nanotube regarding the enhancement effect of CFRP aircraft winglet. First of all, the analysis of the force state of the aircraft winglet, the unidirectional and orthogonal CFRP aircraft winglet at normal temperature, and low- temperature cycling is established based on the principle of classic laminates and statics. The wing cantilever bending critical failure stress mechanics model provides a theoretical basis for the influence of low- temperature cycles on aircraft winglets. Secondly, verifying the correctness of the above-mentioned mechanical model, the CFRP aircraft winglet was studied through bending stress analysis, stress- displacement curve analysis, and sample topography analysis. Finally, the equipment for preparing embedded carbon nanotubes CFRP composite material was designed to ensure the accuracy of the test piece and explored the effect of embedded carbon nanotubes on the CFRP aircraft winglet. The main reason for the weakening of the winglet cantilever anti-bending strength is the fibre. During the low-temperature cycle, the residual stress generated by the aircraft winglet fiber’s repeated damp and heat deformation is too weak to increase the wing's cantilever bending failure critical stress. The enhanced result of the cantilever anti-bending ability and the microscopic mechanism of action provides the basis of the carbon nanotube reinforcement medium to the CFRP aircraft winglet development.&lt;/div&gt;&lt;/div&gt;

Triple-wavelength quantitative phase imaging with refractive index measurement

A method to quantitatively measure the refractive index (RI) and the topography of transparent samples is proposed. Three quantitative phase images at different wavelengths are firstly obtained by using a quadriwave lateral shearing interferometry (QLSI) technique, and then the RIs at the three wavelengths and the physical thickness distribution of the sample are independently calculated with the help of Cauchy's dispersion formula. Neither the highly dispersive medium nor the manual operation of changing the surrounding medium is required. From the measured RIs, the composition of the sample can be identified besides the topography of the sample. Both simulation and experimental results verified the effectiveness and feasibility of the proposed method.

Single-Shot 3D Topography of Transmissive and Reflective Samples with a Dual-Mode Telecentric-Based Digital Holographic Microscope.

Common path DHM systems are the most robust DHM systems as they are based on self-interference and are thus less prone to external fluctuations. A common issue amongst these DHM systems is that the two replicas of the sample’s information overlay due to self-interference, making them only suitable for imaging sparse samples. This overlay has restricted the use of common-path DHM systems in material science. The overlay can be overcome by limiting the sample’s field of view to occupy only half of the imaging field of view or by using an optical spatial filter. In this work, we have implemented optical spatial filtering in a common-path DHM system using a Fresnel biprism. We have analyzed the optimal pinhole size by evaluating the frequency content of the reconstructed phase images of a star target. We have also measured the accuracy of the system and the sensitivity to noise for different pinhole sizes. Finally, we have proposed the first dual-mode common-path DHM system using a Fresnel biprism. The performance of the dual-model DHM system has been evaluated experimentally using transmissive and reflective microscopic samples.

Electrical characterization of tumor-derived exosomes by conductive atomic force microscopy

The physical properties of tumor-derived exosomes have gained much attention because they are helpful to better understand the exosomes in biomedicine. In this study, the conductive atomic force microscopy (C-AFM) was employed to perform the electrical characterizations of exosomes, and it obtained the topography and current images of samples simultaneously. The exosomes were absorbed onto the mica substrates coated with a gold film of 20 nm thick for obtaining the current images of samples by C-AFM in air. The results showed that the single exosomes had the weak conductivity. Furthermore, the currents on exosomes were measured at different bias voltages and pH conditions. It illustrated that the conductivity of exosomes was affected by external factors such as bias voltages and solutions with different pH values. In addition, the electrical responses of low and high metastatic potential cell-derived exosomes were also compared under different voltages and pH conditions. This work is important for better understanding the physical properties of tumor-derived exosomes and promoting the clinical applications of tumor-derived exosomes.

Effect of surface topography and wettability on friction properties of CFRPEEK

The good physical and chemical properties of CFRPEEK make it advantageous as a friction pair for water hydraulic components. This paper investigated the effects of surface topography and wettability on the tribological properties of CFRPEEK and 316 L under water lubrication, with emphasis on four topographies of hemispherical pit, conical pit, ellipsoidal pit and wedge-shaped pit. From the experimental results, the ellipsoidal pit CFRPEEK samples exhibited the best tribological properties and better wettability. An interesting phenomenon was found that when the contact angle of the CFRPEEK sample is small, the friction coefficient and the wear scar depth are also small. In conclusion, taking the ellipsoidal pit as the surface topography of the CFRPEEK sample is conducive to improving its wettability, and promote the formation of stable water film, thereby improving its performance, reducing wear and increasing its service life.

Ultrasonic welding of polyetheretherketone for dental applications

ObjectiveDue to its favorable properties, the high-performance polymer polyetheretherketone (PEEK) is used as a metal-free alternative for the fabrication of denture frameworks. For dental applications, PEEK is available in different colors, such as red or white, by compounding with different fillers. In order to permanently bond such different dental PEEK types together in a denture framework, ultrasonic welding could be a viable process.Therefore, the aim of this study was to determine the optimum processing welding parameters for welding different dental PEEK grades in terms of maximum weld strength. MethodsRectangular plates from three PEEK compounds were prepared according to the dimensions of a removable partial denture (RPD) of PEEK. These were combined in a way that four groups resulted, whereas the combination of pure PEEK served as control. In each group, 5 samples were ultrasonically welded at one of four welding energies using a microprocessor-controlled ultrasonic welder, where the welder was activated only once. Afterwards, the samples were subjected to tensile tests to evaluate the shear bond strength (SBS) of the joint. ResultsIncreasing the welding energy resulted in an increase in the welding time. Accordingly, the increase in the welding energy increased the surface deformation for all tested samples. The shear bond strengths ranged from 4.8 ± 0.68 MPa for samples welded with 50 Ws to 16.37 ± 1.69 MPa for samples welded with 90 Ws. Excessive weld energy of 130 Ws led to a significant decrease of SBS due to a severe indentation and perforation induced by the sonotrode. SignificanceThe SBS and topography of the welded samples were systematically studied and the optimal welding parameters were determined. This could serve as a reference and instruction for clinical applications.

Simultaneous extraction of the elastic-plastic properties of a thin film and its substrate from an identifiability-based design of depth-sensing nanoindentation testing

This work presents an approach to simultaneously identify reliable elasto-plastic properties of a 100 nm amorphous alumina film and plastic properties of its silicon substrate by the Finite Element Model Updating (FEMU) method, using exclusively nanoindentation P−h curves. A 2D axisymmetric finite element model simulates the nanoindentation tests, and the Young's modulus E, the initial yield stress σy and the hardening modulus Hp of the thin film, as well as the yield stress of silicon σys are the parameters to identify. This work relies on a numerical design of experiments carried prior to the identification process. It uses the sensitivity of the nanoindentation force to a variation of the parameters to define an identifiability indicator (I-index) based on the conditioning of the inverse problem. It reflects the stability of the potential solution of the inverse problem. I-index minimisation below a certain value allows to ensure a reliable identification by designing the best combination of experiments in terms of relevant information. I-index analyses values demonstrate that combining Berkovich and cube corner nanoindentation tests at two different indentation depths brings sufficient information to well-conditioned the inverse problem. Indeed, the increased penetration and the varied indenter tip shape induce differentiating factors which activates the substrate effect, or anvil effect, and allow the dissociation of the thin film plasticity from that of the substrate, and thus its identification. The identification procedure of the four parameters carried out with the designed dual nanoindentation test from several starting points reveals that the FEMU method converged to a unique solution. Lastly, the identified parameters are validated by confronting experimental and numerical (i) P−h curves of a Berkovich test on a bulk silicon sample and (ii) residual topographies using a 3D FEM of a Berkovich test on the composite system thin film – substrate.

Degradation Performance Investigation of Hydrothermally Stressed Epoxy Micro and Nanocomposites for High Voltage Insulation.

Epoxy resins have demonstrated remarkable properties with potential for usage as high voltage insulators. However, a loss of these properties has been observed in high temperature and humid environments. In order to enhance the hydrothermal stability of epoxy resins, micro (15% SiO2) and nano (5% SiO2) silica-based composites of epoxy were fabricated and subjected to standard long term and short term accelerated hydrothermal conditions. To analyze the effect of these stresses, the samples were analyzed periodically through Fourier transform infrared spectroscopy (FTIR) for structure analysis; scanning electron microscopy (SEM) for surface analysis of long-term aged samples; and optical microscopy for the surface topography of short-term aged samples. The Swedish Transmission Research Institute (STRI) classification and contact angle measurement techniques were used for hydrophobicity analysis of long-term and short-term aged samples, respectively. After aging in both conditions, the nanocomposite showed better results as compared to the other samples. After 1000 h of aging, it showed HC-5 class of hydrophobicity, whereas EMC and NE degraded to the HC-6. In case of short-term aging, the contact angle decreased to the 64.15° and 75.05° from 104.15° and 114.9° for ENC and EMC, respectively. Also, in terms of structural degradation, ENC showed the highest structural stability after 1000 h of aging with the highest stable peak of aromatic ether at 1300–1500 cm−1. Microscopic observation through scanning electron and optical techniques also revealed superior performance of the nanocomposites.

Tribological Performance of Multiscale Micro-Textured H62 Brass Surface Fabricated by Micro-Milling and Wet Micro-Blasting

Abstract The cylinder block/valve plate interface in the axial piston pump has been proven to be easily worn out, which will increase power loss and reduce its efficiency. The valve plate surface is required to be manufactured with low viscous friction and wear. Multiscale micro-texture has been proven to improve surface tribological properties. However, there are few types of research in the effect of surface topography on the tribological performance of multiscale micro-textured surfaces. The purpose of this study is to explore how the multiscale micro-texture on H62 brass affects its sliding friction behavior on 38CrMoAl. Based on micro-milling and wet micro-blasting, the multiscale micro-textured surface was manufactured on H62 brass. The wet micro-blasting was applied in the H62 brass after the surface micro-texturing. The surface topography of multiscale micro-textured samples processed by three abrasive grit sizes accompanied by two processing times was comprehensively measured in terms of height, feature, functional, and functional volume parameters. The tribological performance of multiscale micro-textured H62 brass was characterized by disk-on-disk frictional experiments. Through analyzing the relationship between surface morphology and tribological properties, the antifriction mechanism of the multiscale micro-textured surface was analyzed from the perspective of 3D surface roughness parameters. The friction coefficient of the multiscale micro-textured surface processed by the combination of micro-milling and wet micro-blasting decreased with the increasing grit size and micro-blasting time.

Influence of Different Nanometals Implemented in PMMA Bone Cement on Biological and Mechanical Properties.

Cemented arthroplasty is a common process to fix prostheses when a patient becomes older and his/her bone quality deteriorates. The applied cements are biocompatible, can transfer loads, and dampen vibrations, but do not provide antibacterial protection. The present work is aimed at the development of cement with antibacterial effectivity achieved with the implementation of nanoparticles of different metals. The powders of Ag, Cu with particles size in a range of 10–30 nm (Cu10) and 70–100 nm (Cu70), AgCu, and Ni were added to PMMA cement. Their influence on compression strength, wettability, and antibacterial properties of cement was assessed. The surface topography of samples was examined with biological and scanning electron microscopy. The mechanical properties were determined by compression tests. A contact angle was observed with a goniometer. The biological tests included an assessment of cytotoxicity (XTT test on human cells Saos-2 line) and bacteria viability exposure (6 months). The cements with Ag and Cu nanopowders were free of bacteria. For AgCu and Ni nanoparticles, the bacterial solution became denser over time and, after 6 months, the bacteria clustered into conglomerates, creating a biofilm. All metal powders in their native form in direct contact reduce the number of eukaryotic cells. Cell viability is the least limited by Ag and Cu particles of smaller size. All samples demonstrated hydrophobic nature in the wettability test. The mechanical strength was not significantly affected by the additions of metal powders. The nanometal particles incorporated in PMMA-based bone cement can introduce long-term resistance against bacteria, not resulting in any serious deterioration of compression strength.

Magnetic force microscopy contrast formation and field sensitivity

The magnetic force microscope (MFM) is an established experimental tool for imaging stray fields with high spatial resolution and sensitivity. The MFM contrast can however contain contributions from the sample topography, variations in the surface Kelvin potential and magnetic contributions arising from grain-to-grain variations of the areal density of the magnetic moment, apart from the contrast generated by the micromagnetic pattern of the sample. Differential imaging techniques can be used to disentangle these contrast contributions. The calibration of the response of the MFM tip on different spatial wavelengths of the field allows a quantitative determination of the magnetic vector field in the plane parallel to the sample surface scanned by the tip. Generally, the tip becomes less sensitive for smaller spatial wavelengths. Obtaining a high spatial resolution thus requires a high measurement sensitivity that can be obtained by MFM operation in vacuum and by using high-quality factor cantilevers. As a result, field sensitivities better than 80μT/Hz can be obtained, even with low magnetic moment tips.

Effects of cutting parameters on the sound level and surface quality of sawn wood

This study investigated the effect of cutting conditions effects on sound level and surface quality in softwood and hardwood. The sound emission level caused by cutting process (band saw) as well as the surface roughness and topography of the wood samples were evaluated. A direct relationship was found between sound emission level and density, moisture content, feeding rate, and dimensions of the samples. Straight cutting of the samples caused less sound emission than cutting in a curved direction. The protective effect of the earmuffs was very significant, reducing the sound emission level from 88 dB to 38 dB. The results showed that with increasing the density and dimensions of the samples, the surface roughness decreased, while with increasing the moisture content and feeding rate, changing the cutting direction from straight to curved, the surface roughness of the samples increased.

Quantitative scanning microwave microscopy of 2D electron and hole gases in AlN/GaN heterostructures

Although the scanning microwave microscope (SMM) is based on the atomic force microscope (AFM), the SMM differs from the AFM by being able to sense subsurface electromagnetic properties of a sample. This makes the SMM promising for in-depth nondestructive characterization of nanoelectronic structures. However, the SMM raw data are convoluted with the sample topography, making it especially challenging for quantitative characterization of nonplanar structures. In this paper, using the topography information simultaneously obtained by the AFM and the in situ extracted probe geometry, we de-embed from the topography-corrupted SMM data the sheet resistance of 2D electron or hole gas (2DEG or 2DHG) buried at the interface of an AlN/GaN heterostructure, including the lateral depletion of the 2DEG from an etched step. The SMM results are validated by Hall-effect measurements. The limitation and possible improvement in the present technique are discussed. With improved setup, the SMM can be used to nondestructively monitor the local sheet resistance of 2DEG or 2DHG during device manufacture. These studies help to pave the way to 3D microwave tomography on the nanometer scale.

AFM Tip Localization and Efficient Scanning Method for MEMS Inspection

Atomic force microscopy (AFM) is widely used in different fields, such as nanotechnology, semiconductor, micro-electromechanical systems (MEMS), bioscience, etc. In the case of obtaining the 3D topography of a large-scale MEMS sample, it is hard to localize the AFM tip position without other auxiliary microscopes in the unknown sample before scanning. Thus, in this paper, the relative probe position on the MEMS layout map can be obtained such that the probe can be moved and placed near the interesting region to start the inspection. However, the AFM scanned images on a MEMS sample typically involve only simple geometries with sparse features, which usually leads to localization difficulty. In this research, an AFM tip localization method was proposed by using the particle filter, referring to the macro-robot simultaneous localization and mapping (SLAM) technique. The AFM scanned images are treated as the unique sensor and the sample layout as the map. The sensor model of the particle filter is based on a feature extraction algorithm. After localization, the interesting area is scanned using a novel efficient scanning method combining online variable speed scan and learning-based feedforward control. In order to verify the effectiveness of the proposed methods, both tremendous simulations and experiments are conducted, and the results of the tip localization and efficient scanning on a MEMS sample are highly promising.

Novel Vertical Scanning Algorithm With Advanced Control to Increase Range and Accuracy of Differential Confocal Microscopy

Differential confocal microscopy (DCM) is a powerful tool for mapping the three-dimensional topography of samples at micron and sub-micron scales. However, the limited vertical scanning range of conventional DCM makes it challenging to obtain three-dimensional profiles precisely. This study sought to mitigate this restriction by developing a novel vertical scanning algorithm as well as an adaptive sliding mode controller based on the internal model principle to precisely track the step scanning trajectory to deal with uncertainties in system parameters, external disturbances, and the hysteresis effect of the piezoelectric scanner in the Z-axis. In experiments, our proprietary DCM system proved highly effective in terms of scanning range, imaging accuracy, and reliability.

Noise Rejection Mode Imaging of Atomic Force Microscope

This paper presents an imaging mode of atomic force microscope (AFM) that is robust to the environmental acoustic noise. AFM operations are sensitive to external disturbances including acoustic noise, as disturbances to the probe-sample interaction directly results in distortions in the sample images obtained. Although conventionally passive noise cancellation has been employed, the passive-noise apparatus limits the function of AFM and its use in emerging applications. Moreover, residual noise still persists. In this work, we propose a noise rejection mode (NRM) of AFM imaging to avoid and eliminate the acoustic-caused disturbance to the imaging process. Contrary to other existing AFM imaging modes, in the proposed NRM approach, the set-point of the feedback loop for tracking the sample topography is adjusted online such that the AFM system is insensitive and thereby, robust to the environmental noise. Then, a feedforward controller is augmented to counter act the noise-caused vibration in the feedback loop. Both the set-point adjustment and the feedforward noise cancellation are implemented through finite-impulse-response (FIR) filters. Experimental examples are presented and discussed to illustrate the proposed technique.

3D surface roughness characteristics for biological applications

This paper deals with the topographic evaluation of samples made from materials applied in biomedicine. Different samples were made from Ti, TiAlV, TiNb and austenitic steel &#8211; Fe were used together with different surface morphology created. These samples were coated with a layer of TiNb alloy. The goal was to measure surface roughness in individual samples of biomaterials and to evaluate a 3D measurement of surface morphology made with a confocal microscope. Another task was to compare with appropriate software the pictures of material topography acquired at lower and higher magnification. Lower (10x) and higher (200x) magnification was used. For measured data evaluation SPIP and Gwyddion software were used. The same method of surface treatment was used but on different samples, which can lead to different results. The values obtained from topography measurements are crucial, but their formulation or evaluation can be affected by different processing methods. Our interest was to find and record the theoretically best procedure for the evaluation of measured data. Then to better understand the cell adhesion and integration of bacteria, we dealt with visualization of topography of given samples.