Surface Topography Images Research Articles

Optical properties of PVP/ZnO composite thin films

Purpose: The aim of the work was the preparation of thin composite layers from PVP polymer doped by ZnO nanoparticles using the spin coating method and the analysis of the applied reinforcing phase on the morphology and optical properties of obtained composites. Design/methodology/approach: To analyse the morphology of thin coatings a technique of surface topography imaging using the atomic force microscopy (AFM) was applied. Analysis of the optical properties was conducted using absorbance spectrum in function of wavelength for all produced thin coatings using UV-Vis spectroscopy. Findings: AFM results show that mass concentration of ZnO nanoparticles of 10% in a solution of PVP/EtOH polymers has a meaningful influence on the morphology of the surface of the PVP/ZnO composite coatings. Using obtained absorbance spectra, the width of the band gap of the manufactured composite coatings were determined which were compared with a band gap values of pure polymer and used reinforcing phase. Practical implications: The analysis of the values of the energy band gap of the manufactured materials showed that both for pure polymer and composite coatings values of energy band gap are similar approx. 4 eV at the same time decrease the degree of absorption of electromagnetic radiation caused by the increasing concentration of the reinforcing phase, which indicates the broad possibilities of application of this type of the material.

Investigation of material removal in vibration polishing of NiCo alloys with millimetre-sized tools

Safety-related plastic parts for the automotive industry require sophisticated, retroreflector mould inserts with a surface roughness in the near optical range (Sa ≈ 20 nm). Due to wear, only a limited number of plastic parts can be moulded and visual inspection and reconditioning of the structured mould insert by manual polishing is tedious and costly. Current work aims to establish an automated process chain as a remedy but due to the limited access to edges and corners, a vibrational motion with a frequency of 133 Hz is applied. This paper investigates the fundamental influence of polishing parameters in this process like polishing pad, grain size of diamond abrasives and polishing time on the material removal and the Archard wear coefficient, which then is applied to estimate the ratio of 2- and 3-body abrasion and compared to the actual surface topography. It was found that the material removal rate is not constant and decreases with longer polishing times. Generally, larger grain sizes and denser polishing pads with shorter fibres cause a higher material removal rate. For all investigated parameter combinations, a 2-body abrasion was present, which is proven by both Archard wear coefficient and surface topography images.

Multiscale characterisation of 3D surface topography of DLC coated and uncoated surfaces by directional blanket covering (DBC) method

Diamond-like carbon (DLC) coated surfaces exhibit anisotropic and multi-scale characteristics, i.e., their roughness change with both scale and direction. However, most currently used standard surface characterisation parameters and methods work well only with isotropic surfaces at a single scale. This problem can be overcome by variance orientation transform (VOT) and directional blanket covering (DBC) methods. Both methods calculate fractal signatures (FSs) in different directions allowing for detailed measurement of roughness of anisotropic and multiscale surfaces. FS is a set of fractal dimensions (FDs) at individual scales, and FD is a measure of surface roughness. High FD values mean rougher surfaces. Unlike other directional FSs methods, e.g., VOT, the DBC method automatically selects scales of calculations. In this study, the DBC method was used to analyse surface topography images of DLC coated and uncoated bearing steel discs of increasing roughness. Its ability to differentiate between two groups of surfaces is evaluated. The results obtained showed that the DBC method can detect differences in roughness at different scales and directions between the DLC coated and uncoated surfaces. This work could lead to applications of the DBC method in modelling of wear and friction behaviour of DLC coated and uncoated surfaces at different scales.

Influence of process parameters of ultrasonic shot peening on surface roughness and hydrophilicity of pure titanium

Ultrasonic shot peening (USP) can be employed to realize surface nanocrystallization and cause the changes of surface roughness and hydrophilicity at the same time, which may help improving the surface biological properties of pure titanium. In this paper, three-dimensional surface topography image, surface roughness and static contact angle of pure titanium treated by USP with different process parameters were obtained by non-contact optical surface profilometer and contact angle meter. Based on the experimental results, the influence rules and mechanism of process parameters, including peening duration, shot diameter, sonotrode amplitude and peening distance, on surface roughness and hydrophilicity of peened pure titanium were studied and the relation between surface roughness and hardness was also analyzed. After that, two relationship expressions were identified: one was between the surface roughness and surface hardness of pure titanium treated by USP while the other one was between the surface roughness and the process parameters with a correlation coefficient equal to 0.9804. According to the Wenzel model, the changes of the roughness factor r and the Young angle θ of pure titanium with different process parameters were calculated, then the influence of the surface roughness and the Young angle θ on the hydrophilicity of pure titanium were also discussed.

Chitosan/zinc oxide-polyvinylpyrrolidone (CS/ZnO-PVP) nanocomposite for better thermal and antibacterial activity

A new biopolymer based ZnO-PVP nanocomposite was successfully synthesized by single step in situ precipitation method using chitosan as biosurfactant, zinc chloride as a source material, PVP as stabilizing agent and sodium hydroxide as precipitating agent. The chemical bonding and crystalline behaviors of chitosan, zinc oxide and PVP were confirmed by FT-IR and XRD analysis. The biopolymer connected ZnO particles intercalated PVP matrix was layer and rod like structure appeared in nanometer range confirmed by HR-SEM and TEM analysis. The surface topography image of CS/ZnO-PVP nanocomposite was obtained in the average thickness of 12nm was confirmed by AFM analysis. Thermal stability of cationic biopolymer based ZnO intercalated PVP has higher stability than CS-PVP and chitosan. Consequently, antimicrobial activity of chitosan/ZnO-PVP matrix acts as a better microbial inhibition activity than PVP-ZnO nanocomposite. The obtained above results demonstrate that CS and ZnO intercalated PVP matrix has better reinforced effect than other components. Therefore, Chitosan/ZnO-PVP nanocomposite may be a promising material for the biomedical applications.

Evolution of Metal Surface Topography during Fatigue

Changes in surface topography reflect the state of fatigue damage. In this paper, a new method to characterize metal surface topography during fatigue has been proposed. Firstly, we acquired surface topography images based on machine vision and separated them into roughness, waviness, and form error images through a shearlet transform. Secondly, we constructed gray co-occurrence matrixes of the obtained surface topography images and calculated the characteristic parameters, such as contrast, correlation coefficient, energy, and entropy for all the original and separated images. Then, taking a Q235 steel specimen as an example for testing, the experimental results and theoretical analysis demonstrate that the parameter contrast increases while energy, correlation coefficient and entropy decrease gradually with number of loading circles, which reach their maximum and minimums before fracture, respectively.

Three-dimensional surface topography of graphene by divergent beam electron diffraction

There are only a handful of scanning techniques that can provide surface topography at nanometre resolution. At the same time, there are no methods that are capable of non-invasive imaging of the three-dimensional surface topography of a thin free-standing crystalline material. Here we propose a new technique—the divergent beam electron diffraction (DBED) and show that it can directly image the inhomogeneity in the atomic positions in a crystal. Such inhomogeneities are directly transformed into the intensity contrast in the first-order diffraction spots of DBED patterns and the intensity contrast linearly depends on the wavelength of the employed probing electrons. Three-dimensional displacement of atoms as small as 1 angstrom can be detected when imaged with low-energy electrons (50–250 eV). The main advantage of DBED is that it allows visualization of the three-dimensional surface topography and strain distribution at the nanometre scale in non-scanning mode, from a single shot diffraction experiment.

Fabrication of Scanning Electrochemical Microscopy-Atomic Force Microscopy Probes to Image Surface Topography and Reactivity at the Nanoscale.

Concurrent mapping of chemical reactivity and morphology of heterogeneous electrocatalysts at the nanoscale allows identification of active areas (protrusions, flat film surface, or cracks) responsible for productive chemistry in these materials. Scanning electrochemical microscopy (SECM) can map surface characteristics, record catalyst activity, and identify chemical products at solid-liquid electrochemical interfaces. It lacks, however, the ability to distinguish topographic features where surface reactivity occurs. Here, we report the design and fabrication of scanning probe tips that combine SECM with atomic force microscopy (AFM) to perform measurements at the nanoscale. Our probes are fabricated by integrating nanoelectrodes with quartz tuning forks (QTFs). Using a calibration standard fabricated in our lab to test our probes, we obtain simultaneous topographic and electrochemical reactivity maps with a lateral resolution of 150 nm.

Nanoscale surface topography imaging using phase-resolved spectral domain optical coherence tomography

Microscopic surface topography plays an important role in studying the functions and properties of materials. Microscopic surface topography measurement has been widely used in many areas, such as machine manufacturing, electronic industry and biotechnology. Optical interferometry is a popular technique for surface topography measurement with an axial resolution up to nanoscale. However, the application of this technique is hampered by phase wrapping, which results in a limited measurement range for this technique. Various digital algorithms for phase unwrapping have been proposed based on the phase continuity between two adjacent points. However, several significant challenges still exist in recovering correct phase with this technique. Optical coherence tomography (OCT) is a non-contact three-dimensional imaging modality with high spatial resolution, and it has been widely used for imaging the biological tissues. In this paper, we demonstrate a method for nanoscale imaging of surface topography by using common-path phase-resolved spectral domain OCT to reduce the influence of phase wrapping. The system includes a superluminescent diode with a central wavelength of 1310 nm and a spectral bandwidth of 62 nm, an optical fiber circulator, a home-made spectrometer, and a reference arm and a sample arm in common-path arrangement. The reference mirror and the sample under investigation are positioned on a same stage in order to further reduce the influence of ambient vibration. The phase difference between two adjacent points is calculated by performing Fourier transform on the measured interferometric spectrum. The phase difference distribution of the surface is obtained first. And then, the surface topography of the sample is constructed by integrating the phase difference distribution. In the traditional methods, phase wrapping occurs if the absolute value of the measured phase is greater than . However, in the present method, phase wrapping occurs if the absolute value of the phase difference between two adjacent points is greater than . The maximal detectable absolute value of the phase difference between two adjacent points increases from for the traditional methods to 2 for the present method. The experimental results indicate that the present system has a high stability and the maximum fluctuation is less than 0.3 nm without averaging. The accuracy of the system is tested with a piezo stage, and the mean absolute deviation of the measured results is 0.62 nm. The performance of the present system is also demonstrated by the surface topography imaging of an optical resolution test target and a roughness comparison specimen. The experimental result shows that the present system is a potential powerful tool for surface topography imaging with an axial resolution better than 1 nm.

Topographical and Chemical Imaging of a Phase Separated Polymer Using a Combined Atomic Force Microscopy/Infrared Spectroscopy/Mass Spectrometry Platform.

In this paper, the use of a hybrid atomic force microscopy/infrared spectroscopy/mass spectrometry imaging platform was demonstrated for the acquisition and correlation of nanoscale sample surface topography and chemical images based on infrared spectroscopy and mass spectrometry. The infrared chemical imaging component of the system utilized photothermal expansion of the sample at the tip of the atomic force microscopy probe recorded at infrared wave numbers specific to the different surface constituents. The mass spectrometry-based chemical imaging component of the system utilized nanothermal analysis probes for thermolytic surface sampling followed by atmospheric pressure chemical ionization of the gas phase species produced with subsequent mass analysis. The basic instrumental setup, operation, and image correlation procedures are discussed, and the multimodal imaging capability and utility are demonstrated using a phase separated poly(2-vinylpyridine)/poly(methyl methacrylate) polymer thin film. The topography and both the infrared and mass spectral chemical images showed that the valley regions of the thin film surface were comprised primarily of poly(2-vinylpyridine) and hill or plateau regions were primarily poly(methyl methacrylate). The spatial resolution of the mass spectral chemical images was estimated to be 1.6 μm based on the ability to distinguish surface features in those images that were also observed in the topography and infrared images of the same surface.

The Challenge of Using Future SWOT Data for Oceanic Field Reconstruction

AbstractConventional altimetry measures a one-dimensional profile of sea surface height (SSH) along the satellite track. Two-dimensional SSH can be reconstructed using mapping techniques; however, the spatial resolution is quite coarse even when data from several altimeters are analyzed. A new satellite mission based on radar interferometry is scheduled to be launched in 2020. This mission, called Surface Water and Ocean Topography (SWOT), will measure SSH at high resolution along a wide swath, thus providing two-dimensional images of the ocean surface topography. This new capability will provide a large amount of data even though they are contaminated with instrument noise and geophysical errors. This paper presents a tool that simulates synthetic observations of SSH from the future SWOT mission using SSH from any ocean general circulation model (OGCM). SWOT-like data have been generated from a high-resolution model and analyzed to investigate the sampling and accuracy characteristics of the future SWOT data. This tool will help explore new ideas and methods for optimizing the retrieval of information from future SWOT missions.

Semiconductor detectors of backscattered electrons in a scanning electron microscope: Characteristics and applications

A configuration of semiconductor detectors of backscattered electrons for a scanning electron microscope (SEM) is presented. The variable width of the detector rings and their oblique arrangement in the electron detection plane increases the detection efficiency by several times, thus making it possible to better separate the contrasts of surface-topography images and the studied-sample composition. By varying the accelerating voltage of the SEM and simultaneously choosing the appropriate detection angles of backscattered electrons, a sharper separation of layer-by-layer images of details of subsurface microstructures can be attained. It is shown that using a semiconductor detector and taking its response function (instrument function) into account, proximate assessments of the thicknesses of ultrathin nanometer-size film coatings on massive substrates can be performed.

Sonochemical Synthesis of Nano-Structured Hydroxyapatite with unique morphologies and Evaluation of Sintering Kinetics

Phase pure hydroxyapatite (HAp) (Ca10(PO4)6(OH)2) ceramic powder was synthesized from the stoichiometric solution of calcium hydroxide and orthophosphoric acid employing sonochemical technique. Crystallinity of the HAp powder is found to be a strong function of amplitude of the ultrasound generator as revealed by XRD patterns and FTIR recorded on the samples prepared using varying amplitudes. Calcination of HAp powder beyond 700°C has resulted in the initiation of sintering as is evident from dilatometric studies and are complimented by the SEM micrographs. Activation energy of sintering of hydroxyapatite pellets using dilatometric sintering kinetic analysis has estimated to be 668±45kJ/mole corresponding to grain boundary diffusion as the prominent mass transport mechanism. Samples exhibited a density of 3.12g/cm3, close to theoretical density (~ 99 %) at the peak temperature of 1200°C. Studies on AC conductivity of the sintered samples exhibited relatively high room temperature conductivity of 5.07x10-8 S/m and a rising trend with temperature probably due to mobility of H+ and OH- ions. Attempts were also made to produce HAp nanorods sonochemically on the ordinary glass substrates immersed in the stoichiometric HAp precursor solution. Surface topographic images of the HAp deposited on glass substrate exhibited nanorods almost individually separated with an average diameter of 50 nm and 200 nm in length providing a process for synthesizing nano-structured HAp with simultaneous deposition exhibiting unique morphologies.

Effects of process and post-process treatments on the electrical conductivity of the PEDOT:PSS films

Poly(3,4-ethylenedioxythiophene) (PEDOT):poly(styrene sulfonate) (PSS) complex is of considerable interest for a variety of applications such as the hole-collecting electrode in solar cells. The conductivity of PEDOT:PSS is low, therefore it is doped or treated with solvents having high boiling points and high dielectric constants resulting in enhancement of conductivity and improvement of efficiency of devises fabricated from this polymer. In this work, to enhance the conductivity of PEDOT:PSS films, N-methylpyrrolidone (NMP) was added into aqueous dispersion of PEDOT:PSS and the conductivity of PEDOT:PSS films prepared on glass was investigated as a function of annealing temperature. The electrochemical properties of untreated and solvent-treated PEDOT:PSS films were studied through cyclic voltammetry. To study the impact of preparation conditions, the films were prepared at different coating speeds and coating times. To investigate the effect of annealing conditions on the conductivity, the films were annealed in an inert environment (N2) and air. Surface topography images obtained by atomic force microscopy showed that addition of NMP into PEDOT:PSS resulted in a uniform distribution of PEDOT domains and smoother phase edges, which could enhance the charge transfer. The conductivity of films increased with lowering the coating speed, which resulted in a higher thickness. Slower coating speeds providing enough time for PEDOT to crystallize led to a uniform distribution of PEDOT regions as compared to faster speeds. Conductivity of the treated films decreased with thermal annealing in both air and N2 indicating that the O2 molecules had no negative effect on the conductivity of PEDOT:PSS films. Hence, the decreased conductivity could be ascribed to interruption of the chains, which changed the morphology and conductivity. The encapsulated films stored in a normal laboratory atmosphere for 30 days exhibited a ~50–60 % decrease in conductivity. However, with applying a second thermal annealing step, the original value of the conductivity was recovered.

Microwave atomic force microscope: MG63 osteoblast-like cells analysis on nanometer scale

In this paper, we report a non-invasive and non-destructive probing method for analyzing the MG63 osteoblast-like cells. High frequency microwave atomic force microscope (M-AFM) can be used to measure the surface topography and microwave image of MG63 cells simultaneously in one scanning process. Under the frequency modulation AFM mode, the M-AFM probe tip can scan above the cell surface, maintaining a constant stand-off distance and the created lateral forces were small enough as not to sweep away or deform the fragile biomolecules. By analyzing the results, quantification such as, the number and distribution of organelles and proteins of MG63 cells as well as their dimension and electrical property information can be characterized. The unique potentials of that M-AFM imaging biological substrates with no damaging manner and nanometer scale resolution, while the original structure and function of the biomolecules during the investigation are preserved, make this technique very attractive to biologists.

Nanostructured fuzz growth on tungsten under low-energy and high-flux He irradiation.

We report the formation of wave-like structures and nanostructured fuzzes in the polycrystalline tungsten (W) irradiated with high-flux and low-energy helium (He) ions. From conductive atomic force microscope measurements, we have simultaneously obtained the surface topography and current emission images of the irradiated W materials. Our measurements show that He-enriched and nanostructured strips are formed in W crystal grains when they are exposed to low-energy and high-flux He ions at a temperature of 1400 K. The experimental measurements are confirmed by theoretical calculations, where He atoms in W crystal grains are found to cluster in a close-packed arrangement between {101} planes and form He-enriched strips. The formations of wave-like structures and nanostructured fuzzes on the W surface can be attributed to the surface sputtering and swelling of He-enriched strips, respectively.

Triboelectric sensor as self-powered signal reader for scanning probe surface topography imaging

We report a self-powered signal reading mechanism for imaging surface topography using a triboelectric sensor (TES) without supplying an external power or light source. A membrane-structured triboelectric nanogenerator (TENG) is designed at the root of a whisker (probe); the deflection of the whisker causes the two contacting surfaces of the TENG to give an electric output current/voltage that responds to the bending degree of the whisker when it scans over a rough surface. A series of studies were carried out to characterize the performance of the TES, such as high sensitivity of 0.45 V mm−1, favorable repeating of standard deviation 8 mV, high Z-direction resolution of 18 μm, as well as lateral resolution of 250 μm by using a probe of size 11 mm in the length and 120 μm in radius. It not only can recognize the surface feature and size but also can perform a surface topography imaging in scanning mode. This work shows the potential of a TES as a self-powered tactile sensor for applications at relatively low spatial resolution.

Surface Potential Investigation of Fullerene Derivative Film on Platinum Electrode under UV Irradiation by Kelvin Probe Force Microscopy Using a Piezoelectric Cantilever

Dynamic-mode atomic force microscopy (DFM) combined with Kelvin probe force microscopy (KFM) has been a powerful tool not only for imaging surface topography but also for investigating surface potential on a nanometer-scale resolution. We have developed DFM/KFM using a microfabricated cantilever with a lead zirconate titanate (PZT) piezoelectric thin film used as a deflection sensor. The observed sample can be in a completely dark environment because no optics are required for cantilever deflection sensing in our experimental setup, which is also equipped with a mechanism to irradiate ultraviolet (UV) light onto the sample. We prepared a platinum-on-silicon substrate and deposited fullerene-derivative (PCBM; [6,6]-Phenyl-C61-Butyric Acid Methyl Ester) film patterns by vacuum evaporation with two shadow masks in crossed directions. The energy band diagram with band-bending, it was created by simultaneously obtaining topographic and surface potential images of the same area using the developed DFM/KFM. [DOI: 10.1380/ejssnt.2015.102]

Correlation of lateral deviation and rotation of the spine in static and dynamic surface topography

The use of SST (Spine and Surface Topography) can significantly reduce the amount of harmful radiation in scoliosis treatment and follow-up. So far the SST examination procedure was only possible in a standing/ upright position of the patient. Newer developments also allow dynamic measurements of the spine in motion. Dynamic SST is a step forward in functional analysis of the spine. Aim Purpose of this study is to investigate the correlation between static and a dynamic SST in scoliosis scanning by 2 selected parameters: spinal deviation and vertebra rotation. The focus of this study is the analysis of range of motion (maxima) in dynamic compared to static measurement results. What does the analysis tell us? Design 18 patients were measured with both static and dynamic SST. The age of the patients was between 25 und 70 years. There are two patients of each age decade. The patients were measured in static 3D (habitual standing position) and with 4D motion (walking on the treadmill/ 3,5km/h). From these two exams per patient the focus was on the two main parameters: analysis of lateral deviation and rotation of the spine and of individual vertebrae. Methods SST uses surface topography imaging for 3D back scanning and techniques creating 3D models of the spine without exposing patients to any ionizing radiation. The spine reconstruction model has been used successfully for more than 20 years in evaluation and treatment of patients with spinal deformities such as scoliosis, lordosis and kyphosis. Dynamic spine analysis is using similar algorithms as used in static measurement. Results We found a significant correlation between the lateral deviation and rotation of the spine in both measurement groups. Those results suggest that static spinal deformities found in a habitual standing position are reflected in a normal walking motion. To a certain degree the dynamic results mirror the static results, tendencies in the maxima in range of motion seems to be an indicator of the severity. Conclusion

Evidence-based nanoscopic and molecular framework for excipient functionality in compressed orally disintegrating tablets.

The work investigates the adhesive/cohesive molecular and physical interactions together with nanoscopic features of commonly used orally disintegrating tablet (ODT) excipients microcrystalline cellulose (MCC) and D-mannitol. This helps to elucidate the underlying physico-chemical and mechanical mechanisms responsible for powder densification and optimum product functionality. Atomic force microscopy (AFM) contact mode analysis was performed to measure nano-adhesion forces and surface energies between excipient-drug particles (6-10 different particles per each pair). Moreover, surface topography images (100 nm2–10 µm2) and roughness data were acquired from AFM tapping mode. AFM data were related to ODT macro/microscopic properties obtained from SEM, FTIR, XRD, thermal analysis using DSC and TGA, disintegration testing, Heckel and tabletability profiles. The study results showed a good association between the adhesive molecular and physical forces of paired particles and the resultant densification mechanisms responsible for mechanical strength of tablets. MCC micro roughness was 3 times that of D-mannitol which explains the high hardness of MCC ODTs due to mechanical interlocking. Hydrogen bonding between MCC particles could not be established from both AFM and FTIR solid state investigation. On the contrary, D-mannitol produced fragile ODTs due to fragmentation of surface crystallites during compression attained from its weak crystal structure. Furthermore, AFM analysis has shown the presence of extensive micro fibril structures inhabiting nano pores which further supports the use of MCC as a disintegrant. Overall, excipients (and model drugs) showed mechanistic behaviour on the nano/micro scale that could be related to the functionality of materials on the macro scale.