Root Mean Square Surface Roughness Research Articles

Valorization of mixed plastics waste for the synthesis of flexible superhydrophobic films

Superhydrophobic surfaces are typically created by enhancing nanoscale roughness or incorporating anti-wetting additives like silanes, nanoparticles, or fluorinated compounds. Limited by the availability of nano-structured templates, simple fabrication, flexibility of the material, and cost-effectiveness, the quest to synthesize superhydrophobic films remains challenging. Herein, we report the valorizing of mixed plastic waste for the synthesis of flexible superhydrophobic films via open-loop recycling. We focused on improving the nanoscale surface roughness of the material by using a series of steps including selective dissolution, thermally induced phase separation, controlled spin-casting, and annealing. We synthesized a two-layered superhydrophobic film with high surface roughness and sufficient mechanical strength, making it suitable for use as a free-standing material. The contact and sliding angles were found to be 159° and 4°, respectively, with an RMS (root mean square) surface roughness of 228 nm. This approach is demonstrated with mixtures of high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polypropylene (PP), which are among the most abundant components of post-consumer plastic waste. Life cycle assessments show that synthesized superhydrophobic films have lower carbon dioxide emissions and embodied energy than virgin PE and PP derived from petroleum. Our design strategy not only yields a superhydrophobic product but also provides an alternative to plastic waste recycling by bypassing cost-intensive sorting techniques.Graphical

Effect of particle surface roughness on the flowability and spreadability of Haynes 230 powder during laser powder bed fusion process

The flowability and spreadability of powders are the important factors for additive manufacturing as these two factors directly impact the powder bed packing density, which further affect the quality and mechanical properties of the built components. The flowability and spreadability of powders are dramatically influenced by particle surface roughness as well as the surface energy. The present research attempt to demonstrate the effect of the particle surface roughness on the flowability and spreadability of Haynes 230 powder. The virgin atomized Haynes 230 powder and the atomized powder after ball milling treatment were employed in the present research. The results show that after ball milling, the surface roughness root mean square (rms) of the initial powder increased from 14.87 nm to 42.54 nm and the surface energy of powder increased from 41.19 mJ/m2 to 77.21 mJ/m2, the rest angle of powder increased 30% and the static cohesion index increased from 0.63 to 2.00. According to the calculated Bog coefficient of the two powders (from 2.85 to 15.56), the increase of particle surface roughness leading to the increase of contact force and non-contact force among particles, which were caused by the increased cohesion, leading to the decrease of powder flowability and spreadability as well as the powder bed packing density.

Toward an Improved Method for Determining the Hamaker Constant of Solid Materials Using Atomic Force Microscopy. III: Experimental Validation of a New Approach-to-Contact Method

A robust experimental validation of an existing approach-to-contact atomic force microscopy (AFM) method for determining the self-Hamaker constant, A11, of a solid, nondeformable material is presented. By explicitly accounting for the underlying surface roughness of a given substrate, this method allows for an estimate of A11 to be obtained from the resulting distribution of AFM cantilever deflections at first contact with the surface, dc. Using this method, the self-Hamaker constants of amorphous silica, stainless steel, and sapphire were determined. Moreover, several plates comprised of the same material, but with different topographies (or values of their root-mean squared surface roughness), were also considered. The values of A11 obtained for these same material plates were found to be in excellent agreement, verifying that this approach-to-contact method properly accounts for the underlying roughness of a given surface. Furthermore, the average value of A11 across all plates for a particular material was in very good agreement with those results previously derived from Lifshitz theory. Finally, the uncertainties in these experimental estimates of A11 were found to be significantly reduced, compared to the uncertainties that arose in some previous approach-to-contact methods.

Optical Interference Filters Combined with Thin Film Residual Stress Compensation for Image Contrast Enhancement

We propose two single-wavelength notch filters and one dual-wavelength (480 and 620 nm) notch filter to enhance image contrast. The stack structure of the notch filters was designed as (Ta2O5/SiO2)4Ta2O5 in Essential Macleod thin film simulation software. Dual-electron-beam evaporation with ion beam-assisted deposition was used to prepare optical interference filters with different center wavelengths. A multilayer notch filter with a center wavelength of 620 nm was deposited on the front surface of the glass, and then a notch filter with a center wavelength of 480 nm was coated on the rear surface of the same glass. The proposed dual-wavelength (480 and 620 nm) notch filter is a combination of two single-wavelength notch filters coated on a double-sided glass substrate to compensate for residual stress. The transmittance, residual stress, and surface roughness of the proposed notch filter were evaluated using different measuring instruments. The experimental results show that the residual stress of the dual-wavelength notch filter could be reduced to 10.8 MPa by using a double-sided coating technique. The root-mean-square (RMS) surface roughness of the notch filters was measured by using a Linnik microscopic interferometer. The RMS surface roughness was 1.80 for the 620 nm notch filter and 2.09 for the 480 nm notch filter. The image contrast obtained with the three different notch filters was measured using an optical microscope and a CMOS camera. The contrast value could be increased from 0.328 (without a filter) to 0.696 (dual-wavelength notch filter).

Freeform reflector light source used for space traceable spectral radiance calibration on the solar reflected band.

For purpose of improving the accuracy of in-orbit radiometric calibration of Chinese Space-based Radiometric Benchmark (CSRB) reference payload on the reflected solar band and reduce resource consumption, this paper proposed a freeform reflector radiometric calibration light source system based on the beam shaping characteristics of the freeform surface. The design method of initial structure discretization based on Chebyshev points was used to design and solve the freeform surface, and the feasibility of the design method was verified by optical simulation. The designed freeform surface is machined and tested, and the test results show that the surface roughness root mean square (RMS) of the freeform reflector is 0.61 μm, which indicates that the continuity of the machined surface is good. The optical characteristics of the calibration light source system are measured, the results show that the irradiance uniformity and radiance uniformity are better than 98% in the effective illumination area of 100 mm × 100 mm on the target plane. The constructed freeform reflector calibration light source system can meet the requirements of large area, high uniformity and light weight for onboard calibration of the payload of the radiometric benchmark, improving the measurement accuracy of spectral radiance on the reflected solar band.

Simulation method of performance of X-ray focusing mirror under actual surface state used in FXT on board EP satellite

The Follow-up X-ray Telescope (FXT) is one of the main payloads on board the Einstein probe satellite. In order to obtain data with high signal-to-noise ratio and realize high-precision positioning of the sources, FXT adopts the Wolter-I X-ray focusing optical system which has been wildly used in X-ray astronomy. According to the principle of Wolter-I and combining the actual manufacture characteristics, we simulate several key parameters affecting the optical quality by Monte Carlo simulation algorithm, such as surface roughness Root-Mean Square (RMS) and surface profile error. The effect of each parameter is analyzed according to the simulation results. Then, the simulation method is verified by the test results of the focusing mirrors provided by PANTER laboratory, and the surface profile error parameters are restricted. The simulation results of the half energy width of the structural-thermal module mirror are basically consistent with the test results. This method can be effectively applied to the later study of focusing mirror manufacture and can accumulate experience for testing and calibrating FXT focusing mirrors. Furthermore, combining the tested calibration data, some key performance of the mirrors can be obtained by this simulation method, such as the effective area, vignetting and the point spread function, which can compose the on-orbit calibration database.

Evaluating Rail Surface Roughness from Axle-Box Acceleration Measurements: Computational Metrology Approach

This study develops a new methodology based on computational metrology techniques to measure rail surface roughness from vertical axle-box accelerations. A VIA rail passenger rail car, operating in eastern Ontario, Canada, was instrumented with accelerometers on the car body, trucks, and axle-boxes. The rail surface was measured by a heavy track geometry inspection car. A Gaussian filter was applied to the measured rail surface data and the rail surface roughness was quantified by the root mean square (RMS), as recommended by ISO 11562 for evaluating engineering surfaces. Values of rail surface RMS roughness calculated from axle-box accelerometer data are verified with the measured surface RMS roughness. The overlap ratio and length of the moving window over which the rail surface RMS roughness is calculated are studied with respect to roughness wavelengths, statistical considerations, and maintenance planning purposes. The effect of rail car operating speed as well as the difference between axle-box accelerations measured at two axles of the instrumented rail car on the accuracy of estimating the rail surface RMS roughness are assessed. Filtering techniques and application limitations for calculating roughness are also discussed. The results of this study suggest axle-box acceleration data provide a useful assessment of rail surface roughness for the typical wavelengths between 3 and 25 m and a complementary technique to light and heavy track geometry inspections.

Residual-Solvent-Induced Morphological Transformation by Intense Pulsed Light on Spin-Coated and Inkjet-Printed ZnO NP Films for Quantum-Dot Light-Emitting Diodes.

It was demonstrated through a comparison between the spin-coated and inkjet-printed quantum-dot light-emitting diodes' (QLED) performance analysis outcomes that the annealing temperature of a zinc oxide nanoparticle (ZnO NP) electron transport layer (ETL) optimized for intense pulsed light (IPL) via a post-treatment differs depending on the film-formation method used. For a naturally dried ZnO NP ETL formulated without annealing, different film morphologies were observed according to the film-formation method of spin coating and inkjet printing, and the surface-roughness root mean square (RMS) value was increased in an IPL post-treatment due to unevaporated residual solvent. Based on this phenomenon, we classified and analyzed different film profiles according to the deposition method, the presence or absence of annealing, and the annealing temperature.

Plasma-enhanced Si-SiC low-temperature bonding based on graphene composite slurry interlayer

Recently, silicon carbide (SiC) has replaced silicon (Si) as a potential material for next-generation power devices. In this study, a Si-SiC low-temperature bonding method based on graphene composite slurry as an interlayer was developed. Ar plasma was used to treat the surfaces of Si and SiC to improve surface hydrophilicity for higher strength bonding. With the increase of discharge power, the root-mean -square (RMS) surface roughness of Si and SiC has obviously increased and the bonding quality was also greatly improved. For 70 W discharge power, the RMS surface roughness values of Si and SiC were 3.22 nm and 1.67 nm respectively, and the bonding strength reached approximately 10 MPa. Through SEM interface analysis, it can be found that a seamless bonding interface was obtained using this bonding process.

Alignment of linear polymeric grains for highly stable N-type thin-film transistors

Summary Temperature-insensitive properties are attractive for most electronics, including polymeric semiconducting devices. Especially, polymeric field-effect transistors (FETs) with high mobility have been important research targets due to their broad applications. However, polymeric FETs with stable charge transport operating at extremely cold or hot zones are faced with enormous challenges. In this study, the polyacrylonitrile was found to significantly tune the sizes of pre-aggregates of polymers in solutions and the crystallinity of the polymeric films. The orientation of 5–25 μm linear grains in the films were prepared through the bar-coating process with polyacrylonitrile as an additive, which stabilized the electron mobility over a wide range of temperatures. The linear-grain morphology of the film contributed to reducing the holes and grain boundaries in the transport paths of carriers. Typically, the top-gate FETs based on P(NDI2OD-T2) displayed a stable electron transporting behavior from 200 to 460 K, with mobility greater than 3.5 cm2V−1s−1.

High performance InGaAs channel MOSFETs on highly resistive InAlAs buffer layers

We investigated the effect of growth temperature on the structural and electrical properties of InAlAs layers grown on InP (100) substrates by metalorganic chemical vapor deposition (MOCVD) method. Flat surface morphology of InAlAs layers with root mean square (RMS) surface roughness values below 0.4 nm were obtained at 500 °C and 660 °C, while RMS surface roughness values of InAlAs layers grown in the region of intermediate temperature increase from 0.7 nm at 540 °C to 3.9 nm at 620 °C with increasing growth temperature. This increase in surface roughness is caused by the phase separation of the InAlAs layer, which is divided into In-rich and Al-rich column regions. The resistivity values of the InAlAs layers grown at 500 °C and 660 °C, in which the phase separation was not observed, were analyzed by the transmission line method (TLM) and those values were ~1 × 104 Ω·cm and 0.06 Ω·cm, respectively. We propose that oxygen atoms being incorporated into InAlAs layers during growth were the cause effect explaining the change in resistivity depending on the growth temperature. In order to evaluate high-resistivity InAlAs layers grown at 500 °C for a buffer layer of devices, we fabricated InGaAs-channel metal oxide field effect transistors (MOSFETs). The on/off current ratio values obtained from ID-VG transfer measurement was a value of 6.10 × 105, indicating a high-performance characteristic.

Enhanced melting flow and vaporization model and its applications in pulsed laser polishing on mold steel.

A developed three-dimensional finite element model to describe surface profiles and root mean square (RMS) roughness by pulsed laser polishing based on the melting flow and vaporization removal mechanism is innovatively presented. In this paper, we indicate that the melting flow and vaporization removal are the primary mechanisms in the laser polishing process and successfully simulated the S316 mold steel pulsed laser polishing via the finite element method. Notably, vaporization removal, vaporization expansion, and plasma impact pressure, which is based on the Navier-Stokes equation, continuity equation, and Marangoni effects, are crucial factors, which are creatively taken into account in this model. Besides, due to the physical parameters changing with temperature, it is critical to considering the temperature-dependent density, specific heat capacity, thermal conductivity coefficient, dynamic viscosity, and tension coefficient to make the simulation results and model accurately. In addition, the tailored model can predict the theoretical polishing surface profiles and RMS roughness based on the melting flow and vaporization removal mechanism. Regarding the single pulse laser polishing, we investigated the surface profiles and RMS roughness on different single pulse energy and pulse width. In summary, it is expected that this study could provide a theoretical reference regarding the laser polishing metals and pave the way for laser manufacturing in various industrial applications.

Conformal smoothing of mid-spatial frequency surface error for nano-accuracy Continuous Phase Plates (CPP)

This paper presented a conformal smoothing theory, and smoothing capability evaluation was established on the proposed theory. According to pressure distribution model, processing parameters have been optimized and the CPP sample with a size of 340 × 340 mm was applied in conformal smoothing. The middle spatial frequency was effectively corrected with the total polishing time of 750 min, and energy was constringed 32.2 times (improved from 57.68 nm2·mm to 1.79 nm2·mm). Meanwhile, surface roughness RMS (root mean square) maintained at the same scale (changed from 265.4 nm to 265.2 nm). Parametric conformal smoothing was proven to be an effective method to control the middle spatial frequency error of CPPs.

Reduction of surface roughness by modification of step-bunched aluminum nitride layers towards step-flow morphology

Conventional aluminum nitride (AlN) template fabrication techniques, like hydride vapour phase epitaxy or AlN growth on patterned sapphire substrates, usually lead to step-bunched template surfaces. The resulting macrosteps cause emission broadening or even multiple-peak characteristics of ultraviolet light-emitting diodes (UV LEDs) fabricated on such AlN templates. In order to reduce these macrosteps and to provide a smoother surface, even without the need of a thick AlN deposition, a two-layer growth procedure is reported here. A three-dimensional (3D) – twodimensional (2D) sequential growth initiates a significant modification of the previous AlN surface morphology and simultaneously limits the evolving tensile strain. A primarily step-bunched surface with a surface roughness root mean square of 1.8 nm is successfully reduced by the two-layer growth procedure down to 0.8 nm, without any film cracking. This distinct roughness reduction of more than 50% is achieved within an AlN thickness of only 1.3 µm. With a smoother surface, the electroluminescence characteristic of a UV LED structure is substantially improved. Instead of a double-peak emission, typical for LEDs grown on step-bunched templates, a single-peak emission and lower spectral width were achieved, indicating the high potential of the suggested two-layer technique for improving performance.

Experimental investigation of carbonate wettability as a function of mineralogical and thermo-physical conditions

Precise characterization of carbonate wettability is challenging and is broadly debated in recent past. While carbonates are known to be oil-wet, the influence of complex mineralogy, surface chemistry, and surface topographic features (e.g. surface roughness) on carbonate wettability did not receive much attention. Furthermore, despite scores of publications analyzing the influence of operating pressure and temperature on carbonate wettability, there are several contradictory trends. Therefore, to address these uncertainties associated with carbonate rock wettability, we report experimental observations of contact angles (θ) for carbonate/crude-oil/brine systems on five different carbonate samples (four real carbonate rocks and a pure calcite mineral) as a function of pressure, temperature, as well as variable mineralogy. In addition, the RMS (root mean square) surface roughness and the pertinent 2D and 3D surface topographic profiles of these rock samples were analyzed and correlated with the observed wetting behaviors. We find that increase in pressure results in an increase in θ in the low-pressure range, while relatively stable θ in high-pressure range. However, the observed θ values, follow both increasing and distinct trends with respect to temperature. Further, surface chemistry of samples suggest that calcite-based samples are relatively more hydrophilic compared to dolomitic carbonates. In addition, the RMS roughness and the corresponding 3D topographic profiles suggest that the samples with abundance of peaks demonstrated much higher θ values. These results may lead to a better understanding of the wider variability associated with the wettability behavior of carbonate rocks.

Morphology, electrical and optical properties of magnetron sputtered porous ZnO thin films on Si(100) and Si(111) substrates

In this work, we reported the effects of annealing temperature on the morphologies and electrical and optical properties of sputtered ZnO thin films grown on Si(100) and Si(111) substrates. Annealing at 600 °C leads to smooth and porous ZnO thin films (internal holes) with root mean square (RMS) surface roughness values of 0.56 and 0.81 nm on Si(100) and Si(111) substrates, respectively. In contrast, 900 °C annealing results in slightly rough, porous ZnO thin films with exposed holes and RMS surface roughness values of 6.1 and 6.5 nm for Si(100) and Si(111) substrates, respectively. XPS and photoluminescence spectra show that a high annealing temperature reduces the number of oxygen vacancies/defects and Zn defects and slightly decreases the binding energy for the Zn 2p3/2 peak. Meanwhile, metallic Zn was present in porous ZnO thin films grown on Si(111) substrates annealed at 600 °C but disappeared as the annealing temperature increased to 900 °C. In addition, the porous ZnO thin film grown on Si(111) substrate annealed at 900 °C exhibited the best optical properties and had only a few interstitial oxygen defects.

Optimization of ultrafast laser parameters for 3D micromachining of fused silica

We present an optimization study on laser parameters for 3D micromachining of fused silica to achieve critical goals for practical applications including high surface quality, high volume production, and complex surfaces by ultrafast laser direct writing assisted chemical etching. We conducted experiments on laser pulse width of 300 fs and 1 ps, pulse energy ranging from 0.1 µJ to 1.6 µJ, three different polarizations (circular, parallel and perpendicular) and number of overlapped pulses from 3 to 10,000 at 1030 nm with up to 2 MHz repetition rate to investigate their effect on nanogratings and one dimensional (1D) channel and two dimensional (2D) planar surface selective etching on 1 mm thick fused silica. In one configuration, we achieved 21.8 nm RMS surface roughness with 80 µm Gaussian filtering and in another configuration, we estimated the maximum writing speed to be 1.25 m/s for given 2 MHz repetition rate with less than 400 nm filtered root mean square (RMS) surface roughness at a 1 mm2 area which covers the thickness of the glass.

Growth Behavior of Au Films on SiO2Film and Direct Transfer for Smoothing Au Surfaces

Direct transfer of Au films deposited on smooth SiO2film with RMS (root mean square) surface roughness of 0.24 nm was investigated with the aim of generating smooth Au surfaces. Deposited Au films with different thicknesses were transferred to rough Au surfaces on target substrates at room temperature with a contact pressure of 50 MPa. Observation of the growth behavior of the deposited films revealed that they formed a continuous structure when their nominal film thickness was around 15 nm or above. The transfer of continuous Au films with a thickness of 20, 51, or 102 nm reduced the RMS roughness of the rough Au surfaces from 1.6 nm to 0.4 nm. In contrast, the transfer of Au films with a thickness less than 5 nm increased their surface roughness. This direct transfer technique should thus be useful for low temperature bonding.

Highly efficient flexible organic photovoltaics using quasi-amorphous ZnO/Ag/ZnO transparent electrodes for indoor applications

We report the indoor performance of flexible organic photovoltaic devices utilizing quasi-amorphous ZnO/Ag/ZnO as the transparent conducting electrode. A ZnO/Ag/ZnO electrode with specific thickness values of 40/9/50 nm provides excellent transparent conducting electrode properties with transmittances up to 92% in the visible region, a sheet resistance of 4.8 Ω/sq, and a root-mean squared surface roughness value of 2.1 nm. In addition, the micro-cavity effect and quasi-amorphous structural properties of the ZnO/Ag/ZnO electrode allow further enhanced light absorption and mechanical stability, respectively. Poly (3-hexylthiophene):indene-C60 bisadduct photoactive layer-based inverted organic photovoltaics with the ZnO/Ag/ZnO (40/9/50 nm) electrode yield an averaged power-conversion efficiency of 12.3% under a light-emitting diode lamp with a luminance of 500 lux, which is 20% greater than the power-conversion efficiency value of the reference organic photovoltaics with an indium tin oxide electrode. Furthermore, the same organic photovoltaics on flexible polyethylene terephthalate substrates exhibit excellent mechanical stability (i.e., 92% of the initial power-conversion efficiency value is maintained even after 400 bending cycles with a bending radius of 9.55 mm), with averaged power-conversion efficiency values of 10.2% under the 500-lux light-emitting diode.

Development of Flower Like Hierarchical Thiourea Loaded Titania–Poly Vinyl Alcohol Nano Composite Coatings for the Corrosion Protection of Mild Steel in Hydrochloric Acid

A stable, thiourea doped titania–poly vinyl alcohol (PVA) hybrid nanocomposite anticorrosion coating on mild steel has been developed via sol–gel dip-coating method. For comparative studies, bare titania sol–gel is coated over mild steel and evaluated using electrochemical methods. To investigate structure and morphology of coating, fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectrometry (EDX), X-ray diffraction (XRD), UV absorbance spectra, and atomic force microscopy (AFM) techniques were employed. Effect of drying temperature of coated samples at 100, 200 and 300 °C on the corrosion protection nature was analysed. The coating dried at 200 °C exhibit maximum corrosion protection ability. Thiourea at 1, 1.4, 1.8 wt% were incorporated into titania–PVA hybrid nanocomposite and the corrosion protection ability of these sol–gel coatings were evaluated by weight loss, impedance spectroscopic studies (EIS), and polarization measurement in 1 M HCl solution. FESEM shows that thiourea and the modifier PVA results the cracked bare titania coating to a flower like hierarchical distribution all over the surface of mild steel, AFM analysis revealed that the surface was found to be spiky in nature with surface roughness root mean square (rms) value of 0.33 µm and exhibit better corrosion resistance in 1 M HCl solution. The results of the study reveal that there is an optimum (1.8 wt%) of thiourea loading for beneficial effects on the corrosion resistance and increase the efficiency significantly (97%).This simple, facile and eco-friendly method has great potential to replace environmentally hazardous chromate conversion coatings. Moreover the modified coating on metal offers attractive protection efficiency on extending the exposure period in 1 M HCl to 70 days, which is far superior to the conventional sol–gel coating which losses efficiency day by day. The protective layer consists of a compact structure of hybrid PVA–titania and electron rich thiourea molecules on the surface of the metal offering significant physical barrier against the attack of corrosive ions from acid solution.