Varying Degrees Of Surface Roughness Research Articles

The effect of step-flow growth on the surface morphology and optical properties of thick diamond films

Thick diamond films are needed for high power device applications. One approach is to grow via the step-flow growth mode on miscut substrates. In this paper we correlate variations of surface morphology and optical properties of a 250 μm-thick undoped diamond layer, grown at a rate of 10.4 μm/h, on a (001) diamond substrate with a miscut angle of 10 degrees towards a <010> direction. The epilayer surface comprises regions with island growth on (001) planes, and regions parallel to the miscut substrate surface exhibiting step-bunching and faceting and resulting in various degrees of surface roughness. The optical properties exhibit a combination of sharp and broad luminescence peaks, which are found to be specific to growth morphology and to the nitrogen content in the near-surface region.

Quantifying the Impact of the Surface Roughness of Hexagonal Ice Crystals on Backscattering Properties for Lidar‐Based Remote Sensing Applications

AbstractImpacts of small‐scale surface irregularities, or surface roughness, of atmospheric ice crystals on lidar backscattering properties are quantified. Geometric ice crystal models with various degrees of surface roughness and state‐of‐the‐science light‐scattering computational capabilities are utilized to simulate the single‐scattering properties across the entire practical size parameter range. The simulated bulk lidar and depolarization ratios of polydisperse ice crystals at wavelength 532 nm are strongly sensitive to the degree of surface roughness. Comparisons of these quantities between the theoretical simulations and counterparts inferred from spaceborne lidar observations for cold cirrus clouds suggest a typical surface‐roughness‐degree range of 0.03–0.15 in the cases of compact hexagonal ice crystals, which is most consistent with direct measurements of scanning electron microscopic images. To properly interpret lidar backscattering observations of ice clouds, it is necessary to account for the degree of surface roughness in light‐scattering computations involving ice crystals.

Spatial Frequency Effective for Increasing Perceived Glossiness by Contrast Enhancement.

It has been suggested that luminance edges in retinal images are potential cues for glossiness perception, particularly when the perception relies on low-luminance specular regions. However, a previous study has shown only statistical correlations between luminance edges and perceived glossiness, not their causal relations. Additionally, although specular components should be embedded at various spatial frequencies depending on the micro-roughness on the object surface, it is not well understood what spatial frequencies are essential for glossiness perception on objects with different micro-roughness. To address these issues, we examined the impact of a sub-band contrast enhancement on the perceived glossiness in the two conditions of stimuli: the Full condition where the stimulus had natural specular components and the Dark condition where it had specular components only in dark regions. Object images with various degrees of surface roughness were generated as stimuli, and their contrast was increased in various spatial-frequency sub-bands. The results indicate that the enhancement of the sub-band contrast can significantly increase perceived glossiness as expected. Furthermore, the effectiveness of each spatial frequency band depends on the surface roughness in the Full condition. However, effective spatial frequencies are constant at a middle spatial frequency regardless of the stimulus surface roughness in the Dark condition. These results suggest that, for glossiness perception, our visual system depends on specular-related information embedded in high spatial frequency components but may change the dependency on spatial frequency based on the surface luminance to be judged.

Surface heterogeneity: a friend or foe of protein adsorption - insights from theoretical simulations.

A lack in the detailed understanding of mechanisms through which proteins adsorb or are repelled at various solid/liquid interfaces limits the capacity to rationally design and produce more sophisticated surfaces with controlled protein adsorption in both biomedical and industrial settings. To date there are three main approaches to achieve anti biofouling efficacy, namely chemically adjusting the surface hydrophobicity and introducing various degrees of surface roughness, or a combination of both. More recently, surface nanostructuring has been shown to have an effect on protein adsorption. However, the current resolution of experimental techniques makes it difficult to investigate these three phase systems at the molecular level. In this molecular dynamics study we explore in all-atom detail the adsorption process of one of the most surface active proteins, EAS hydrophobin, known for its versatile ability to self-assemble on both hydrophobic and hydrophilic surfaces forming stable monolayers that facilitate further biofilm growth. We model the adsorption of this protein on organic ligand protected silica surfaces with varying degrees of chemical heterogeneity and roughness, including fully homogenous hydrophobic and hydrophilic surfaces for comparison. We present a detailed characterisation of the functionalised surface structure and dynamics for each of these systems, and the effect the ligands have on interfacial water, the adsorption process and conformational rearrangements of the protein. Results suggest that the ligand arrangement that produces the highest hydrophilic chain mobility and the lack of significant hydrophobic patches shows the most promising anti-fouling efficacy toward hydrophobin. However, the presence on the protein surface of a flexible loop with amphipathic character (the Cys3-Cys4 loop) is seen to facilitate EAS adsorption on all surfaces by enabling the protein to match the surface pattern.

Hydrodynamic Performance Produced by Nanotexturing in Submicrometer Clearance With Surface Roughness

Surface texturing is a promising way to expand the hydrodynamic lubrication regime and thereby modify the tribological properties of sliding surfaces. Spiral-groove textures in particular have attracted much attention over the past several decades because they produce a thicker lubrication film in the gap. However, no research has been reported on the effect of periodic texturing with a several 100 nm depth on hydrodynamic performance in submicrometer clearance with surface roughness. The purpose of the study reported here was to investigate the effect of such nanotexturing on hydrodynamic performance. This was done by conducting ring-on-disk friction tests, focusing on the existence of surface roughness in the narrow clearance. The samples were rings with various degrees of surface roughness and disks with spiral-groove textures produced by femtosecond laser processing. The friction coefficients experimentally obtained were plotted as a Stribeck curve and compared with a theoretical one calculated using a Reynolds equation formulated from two physical models, the Patir–Cheng average flow model and a sinusoidal wave model. The results showed that surface roughness did not affect the friction coefficient in the hydrodynamic lubrication regime. However, the hydrodynamic lubrication regime gradually shrank with an increase in surface roughness, and mild transitions to the mixed lubrication regime were observed at higher rotational speeds. The minimum clearances reached at the transition speed were almost the same, about 200–300 nm, for all experiments regardless of surface roughness.

The ice friction of polymeric substrates

A fixture has been designed and utilized in conjunction with a conventional rotational rheometer to measure and study the mechanisms of friction of polymeric surfaces (ultra-high molecular weight polyethylene, polytetrafluoroethylene and polymethylmethacrylate) on ice. Ice friction experiments were performed at various sliding velocities (from 0.0079 to 1.96m/s), temperatures (from −25°C to −1.5°C), and various degrees of surface roughness. It was found that the magnitude of the sliding velocity and temperature play important roles in ice friction. Friction coefficient decreases with increasing temperature at high sliding velocities (from 0.79 to 1.96m/s) due to surface lubrication. However, at lower sliding velocities (from 0.0079 to 0.079m/s) the friction coefficient initially decreases and then increases due to the modification of the real contact area on the ice surface. The ice friction coefficient was found to be nearly independent of relatively small differences in surface roughness. Finally, the ice friction coefficient of three polymer substrates exhibiting very different static contact angles, from hydrophilic to hydrophobic, was found to scale inversely with their water static contact angle.

Efficiency and Wear Behavior of the Abrasive Flow Machining Processing

This study attempts to determine how AFM affects the polishing of complex hole to achieve a smooth surface by examining WEDM efficiency when cutting a complex hole for various degrees of surface roughness. This research showed the complex holes with the chain shape of the mold steel were cut by WEDM first, however, there were three kinds of the average roughness in the hole surface (1.3μm Ra, 0.8μm Ra and 0.4μm Ra) when three cutting processes of WEDM were used to manufacture the complex holes. Then silicon carbon (SiC) or diamond abrasive (DA) mixed with the silicone gel was utilized as abrasive medium to polish these holes, machining processes were finished when the surface roughness of the complex holes were decreased to the steady values in AFM. Finally, three surface roughness of the complex hole in the different positions would be used to judge the finishing surface was smooth or not, and machining time of the complex holes between WEDM and AFM was utilized to evaluate the efficiencies of these process when the surface of the complex holes had uniform roughness after machining. The results showed that surface roughness would not easily uniform after AFM until the cutting roughness, produced by WEDM, reduced to 0.4μm Ra when SiC was utilized as abrasive. But the surface roughness would uniform after AFM only the cutting roughness reached 0.8μm Ra when DA was used as abrasive, and the total machined time to a uniform roughness (WEDM+AFM) was the less (45 minutes) when the cutting roughness with 0.8μm Ra was utilized as original surface roughness.

Effects of Surface Processing on the Response of CZT Gamma Detectors: Studies with a Collimated Synchrotron X-Ray Beam

Using a microscale X-ray mapping technique incorporating a synchrotron beam, we are able to reveal the fine details of the surface properties in cadmium zinc telluride (CZT) semiconductor detectors. A detector, with various degrees of surface roughness, was irradiated by a high-spatial-resolution X-ray beam. The detector's response was analyzed and displayed as a two-dimensional (2-D) map, and the charge collection was obtained from the peak positions in the spectra versus the beam's location, which reflects the local material properties. We noted the correlation between the 2-D image and the spectral response of the charge collection at different locations on the surface area, which indicates that a rough surface tends to contain trapping centers, thereby enhancing leakage current and distorting the signal. We also discuss our observations on the transition effect at the boundary area of a rough and a smooth surface under identical conditions.

Modeling the effects of surface roughness on the emissivity of aluminum alloys

This study explores the relationship between the emissivity of aluminum alloy surfaces and surface roughness. Two methods are discussed which yield good overall predictions of the emissivity of rough surfaces. One method consists of using a mathematical multispectral radiation thermometry (MRT) model for the emissivity and determining both the surface temperature and the empirical constants in the emissivity model from radiance measurements. This method requires new emissivity constants to be determined for each surface topography. This study also presents an alternative method for determining the emissivity of rough surfaces. This method relies on determining the emissivity characteristics of a single reference surface and inferring the emissivity of any other rough surface of the same material by relating a surface roughness function (determined by surface topography instrumentation) of the rough surface to that of the reference surface. Using data for AL 7075 with various degrees of surface roughness, this method is shown to yield better accuracy than the first method.

Ti及Ti-6 Al-4V合金表面粗糙度對類造骨U-2 OS細胞初期貼附及增殖之影響

The effect of surface roughness of Ti and the Ti-6AI-4V alloy on the initial adhesion and proliferation behavior of osteoblast-like U-OS cells was investigated. Different numbers (#120, #600, and #1 500) of silicon carbide paper and alumina powder at 1-pm particle size were used to prepare specimens with various degrees of surface roughness. Results showed that surface roughness had a significant influence on the optical density (OD) value of attached cells after a 2-hour incubation (Ti,p＜0.001;Ti6AI4V,p ＜0.01). Contact guidance of cells was observed on #120 and #600 specimens for Ti and the Ti6AI4V alloy. Polished specimens exhibited the worst adhesive behavior of cells. Specimens with a roughness(Ra) of around 0.14μm had the highest OD value. Furthermore, surface roughness had a statistically marginal influence on the number of the attached cells after a 3-day incubation (Ti,p=0.0689;Ti6AI4V,p=0.0503).The highest number of the attached cells was found for specimens with a roughness (Ra) of around 0.07μm. From results of this study, we conclude that surface roughness has a statistically significant influence on the initial optical density of osteoblast-like U-2 OS cells cultured on Ti and the Ti6Al4Valloy, and a statistically marginal influence on the number of prdiferating cells.

Effect of surface roughness of porcelain on adhesion of bacteria and their synthesizing glucans

Statement of Problem: In some instances of porcelain restoration, refinishing is inevitable. In terms of plaque accumulation on porcelain, refinishing could be a substitute method for glazing. Purpose: This study compared the amount of adhesion of plaque components (bacterial cells and glucans) on porcelain disks with various degrees of surface roughness to assess the effects of surface roughness on the amount of plaque accumulation. Material and Methods: Radiolabeled cell suspensions were incubated with porcelain disks for 3, 8, and 24 hours at 37°C, and the amounts of adhered cells and glucans were measured by using a liquid scintillation method. Results: The amount of cells and glucans adhered on porcelain increased with incubation time. The surface roughness value and the amount of plaque adhesion decreased with the increase in polishing level. However, the greatest amount of plaque was adhered on glazed surfaces, although their surfaces were smoother than the surfaces polished with 120- or 600-grit abrasive papers. Conclusion: With the exception of glazed surfaces, a positive correlation between surface roughness and the amount of plaque accumulation was observed. Repolishing with a diamond paste would not induce problems of plaque accumulation, compared with an intact glazed surface. (J Prosthet Dent 2000;83:664-7)

Surface design of aramid film for future ME tapes

Surface configurations for aromatic polyamide (aramid) film were investigated, with the aim of improving the surface design of basefilm for future Metal Evaporated (ME) tapes. Characteristics of ME tapes with various degrees of surface roughness were measured in this study. Through this investigation, the surface configuration contributing to maximum output and durability is identified; this configuration involves both spike protrusions and fine protrusions. In addition, narrowing size distribution of fine protrusions considered to be effective in reducing the real contact area, which leads to improved durability.

Nondestructive Measurement of the Subsurface Structure of Biological Material Having Cellular Structure by Using Near-Infrared Spectroscopy

Biological materials–wood is a typical example–are widely used in a state where not only the cellular structure but also its bulky shape is retained. NIRS (near-infrared spectroscopy) may be called for as a promising technique to analyze the physical state of such materials as well as the chemical composition. In this report, the effects of physical conditions found in wood on the absorption of NIR radiation are examined. In the experiments, conifers (Sitka spruce) that had various degrees of surface roughness and different orientations of fibers to the direction of incident light were used. Results of these measurements showed that the orientation of fibers and the surface roughness of wood were directly related to the absorbance. In addition, it became clear that the behavior of diffusely reflected light in wood could be expressed by Kubelka–Munk theory and fell into three categories according to the characteristic of the absorption and scattering coefficient. On the basis of these results, a new concept for the behavior of NIR light passing through material made of hollow fibers has been proposed.

Observation of surface plasmon splitting on Ag(111) by electroreflectance spectroscopy

The spectral dependence of electroreflectance near the surface plasma frequency of Ag(111) has been measured for various degrees of surface roughness. The experiments clearly show a splitting of the surface plasma resonance on increasing the roughness of the sample. The results agree well with a recent theory which predicts a splitting of the surface plasmon dispersion relation on a statistically rough surface.

Effect of surface roughness on surface resistance of plane copper surfaces at millimetre waves

Measurements have been made at 35 GHz of the increase of surface resistance of plane copper surfaces caused by surface roughness. The side walls of an H-guide cavity were ground one-directionally with abrasive papers of various grades. Surface roughness was determined mechanically, optically, and by microphotography. Q factors of the cavity were measured and evaluated and compared for various degrees of surface roughness

A Summary of NACA Research on Heat Transfer and Friction for Air Flowing Through Tube With Large Temperature Difference

Abstract The results of experimental and analytical studies performed at the NACA to determine the heat-transfer and friction coefficients for the flow of air through tubes with large difference in temperature between tube wall and air, (a) for smooth tubes of circular cross section; (b) for tubes of noncircular cross-sectional shapes; and (c) for tubes with various degrees of surface roughness, are summarized. The experiments for the smooth tubes of circular cross section cover a range of tube-wall temperature from 535 R to 3050 R, inlet-air temperature from 535 R to 1500 R, Reynolds numbers from 1000 to 500,000, exit Mach numbers up to 1, and tube length-to-diameter ratios from 15 to 120. Methods of correlating these data are discussed. The tubes of noncircular cross-sectional shape, namely, (a) square, (b) rectangular, and (c) triangular, were investigated at tube wall-to-air temperature differences up to 1200 F and Reynolds numbers between 2500 and 250,000. Three degrees of surface roughness, obtained by machining square threads into the inner surface of the tube, were investigated for temperature differences between the air and tube wall up to 1500 F and Reynolds numbers from 1000 to 350,000.