Dependence Of Surface Roughness Research Articles

Influence of chemistry and surface roughness of various thermal barrier coatings on the wettability of molten sand

High temperature wettability experiments were carried out to investigate how chemistry and surface roughness affect wetting characteristics of molten sand several promising thermal/environmental barrier coatings. Contact angle experiments were performed on varying as-sprayed and polished yttria-stabilized zirconia (YSZ), rare-earth oxide-YSZ (REO-YSZ), and rare-earth silicate coatings subjected to molten synthetic sand at 1260 °C. The results showed that the spreading rate of molten sand was higher on silicate-based environmental barrier coatings (~60°/min) than on Zr-based thermal barrier coatings (~25°/min). Increased surface roughness had opposite effects on the wettability depending on the reactivity of the coatings. Wettability decreased on coatings such as YSZ (which did not react with sand) but increased for REO-YSZ coatings (which formed reaction products with sand). It was found that while the REO-YSZ coatings were able to promote formation of the apatite that performed as a sealing layer to reduce further infiltration, molten sand wetting increased. YSZ was found to have greater wetting resistance in the roughened state while the REO-YSZ coatings had greater wetting resistance in the polished state. Surface energy, microstructure, and molten sand penetration also play a key role in the wetting kinetics and are discussed. This work reveals the dependency of chemistry and surface roughness on influencing the “sandphobicity” (analogous to hydrophobicity) of a material and provides insights for optimizing these variables to realize more “sandphobic” coatings.

Evolution of the mixed mode FPZ and fracture roughness of Beishan granite after coupled thermo-hydro-mechanical treatment

Deep surrounding rocks contain a network of longitudinally intersecting fissures. Exploration of their fracture process zone (FPZ) size evolution during mixed loading and fracture surface roughness after failure has always been a hot topic, especially for coupled thermo–hydro–mechanical (THM) treatment. This study takes Beishan granite as the research object. The fracture surface roughness and FPZ length were obtained using Grasselli statistical and mixed strain–displacement methods. Finally, an electron microscope was employed to observe the fracture surface after failure at different temperatures and loading angles. Results reveal a notable temperature and load dependence of the fracture surface roughness and FPZ length evolution. In the low-temperature stage (25°C–300°C), the mineral primarily exhibited transgranular fractures and the average fracture surface roughness showed a slightly decrease with increasing temperature. In the high-temperature stage (500℃–650℃), the degree of internal damage to the prepared specimens substantially increased, with intergranular fractures being the dominant fracture mode, and rapid roughness growth occurred. Under the same temperature condition, the roughness value was in the order of mode I > mixed mode > mode II. The FPZ length increased, stabilized, and decreased as the load increased. In the low-temperature stage, the FPZ length reached its maximum value at the maximum load, whereas in the high-temperature stage, the FPZ length was fully developed before the peak load. Under the same loading angle condition, the FPZ lengths corresponding to the three loading modes followed the order of mode I < mixed mode < mode II.

ДОСЛІДЖЕННЯ ШОРСТКОСТІ ПОВЕРХНІ ПРИ ОБТОЧУВАННІ ХРОМОМОЛІБДЕНОВОЇ СТАЛІ

Surface roughness is one of the parameters of product quality, that’s why the research of cutting mode impact on surface roughness is a current topic. The diversity of cutting tools and materials to be worked leads to the need for more detailed study of the impact of cutting modes on surface roughness.Previous researches have established that the radius of curvatureof cutting tool and the cutter feed have an impact on surface roughness. There are also studies for assessing cutting speed and cutting depth effects on surface roughness. But these studies are not complete and exhaustive, because they have been done for selected materials, cutting tools and cutting modes.The aim of the research described in the article is a scientific inquiry of cutting mode impact on surface roughness in turning of chromium-molybdenum steel 38ХМand the search for optimal cutting modes for this steel.The mathematical relationship between surface roughness and cutter feed, cutting depth, cutting speed was written in the form of power function. The range of variation was chosen. Regression coefficients were defined on the methodology of full factor experiment of type 23. The constructed mathematical model has been checked for adequacy. The equation of surface roughness dependence on cutting mode in turning of 38ХМsteel was obtained.Finding the best possible combinations of cutter feed, cutting depth, cutting speed values for turning of 38ХМsteel was undertaken using the Taguchi method. It was based on the search for technological modes in which the evaluated quality parameter is least affected by uncontrolled factors.As a result of the research it is established that cutting speed and cutting feed have the greatest impact on surface rough-ness. It is also shown that cutting depth has a negligible impact on surface roughness. It is proved that the machining processed at small cutting depthand small feed and large cutting speed is most appropriate. The optimal cutting modes for turning, providing minimal surface roughness are determined.Thus, the complex use of full factor experiment method and the Taguchi method made it possible not only to obtain the equation for the dependence, but also to determine optimal cutting modes.

Size and pressure dependence lattice thermal conductivity of Wurtzite GaN nanowires

The size and pressure effect on lattice thermal conductivity (LTC) of Wurtzite GaN NWs with diameters of 97, 100, 126, and 160 nm in the temperature range (2–350) K fitted to those reported experimental data. The investigations were based on the Debye-Callaway model along with the Clapeyron and Murnaghan equations, for both longitudinal and transverse modes of phonons. by considering in the calculations, the nanosized dependence of melting temperature, lattice volume, Debye temperature, and group velocity. Nanosized melting temperature is used to calculate its related parameters of melting enthalpy, melting entropy, and surface energy. In this work, the nanosized dependence relation for the Gruneisen parameter gives values of 0.14475 for 160 nm and increases to 0.14535 for 97 nm. While its modification due to the applied pressure reduces its value. The relations are obtained for the nanosized dependence of surface roughness, Casimir length, dislocation concentration and lattice scattering factor, enabling this model to obtain LTC free from fitting parameters. The model was then applied successfully on 50 and 30 nm NWs diameter for this binary semiconductor.

Surface roughness of hardened steel 90MnCrV8 after turning with actively driven tool rotation

With the increase in the use of difficult to machine and hard materials, it is necessary to find new productive ways of machining these materials. Among these technologies, we can also include forced tool rotation turning (ADRT), the easy deployment of which is made possible by the development of CNC machine tools. This non-standard kinematic structure of machining brings many advantages, mainly in increased tool life and lower temperatures in the cutting zone. This technology can be used for the production of parts in the automotive and aerospace industries. In the experiment of the paper, the dependence of surface roughness on cutting speed in turning with forced tool rotation was investigated. A monolithic tool was designed and used for the experiments, which was predicted to have higher strength and reduced recess formation compared to a tool with an interchangeable cutting insert. The measured roughness of the machined materials reached relatively low values, which could be further improved with improvements in the overall process technology system.

ИССЛЕДОВАНИЕ ЗАКОНОМЕРНОСТЕЙ ФОРМИРОВАНИЯ МИКРОПРОФИЛЯ ОБРАБОТАННОЙ ПОВЕРХНОСТИ ПРИ ХОНИНГОВАНИИ С ПРЕДВАРИТЕЛЬНОЙ КРИОГЕННОЙ ОБРАБОТКОЙ

This article is devoted to the study of the regularities of the formation of the microprofile of the treated surface during honing with preliminary cryogenic treatment. The dependence of surface roughness on processing modes during honing with preliminary cryogenic treatment of products from low-carbon steels has been studied. Mathematical models of these processes in the form of regression equations are obtained. Empirical curves of dependencies of the roughness parameter Ra are constructed using the Microsoft Excel 9.0 application package and the MathCAD 15.0 package.

Growth-rate model of epitaxial layer-by-layer growth by pulsed-laser deposition.

We present a numerical model of epitaxial thin-film growth applicable for pulsed-laser deposition on a single crystalline substrate. The model is based on rate equationsdescribing the time development of monolayer coverages and of densities of movable particles on atomically flat terraces. Numerical solution of the equationsshowed that the time dependence of surface roughness obeys a scaling law, the exponent of which depends on probabilities of various atomistic processes included in the simulation model. From the time dependence of monolayer coverages we calculated x-ray diffracted intensity in a quasiforbidden anti-Bragg reflection and showed that its oscillatory behavior is affected by these probabilities as well. The results show the possibility to study atomistic processes during the deposition from the time dependence of the anti-Bragg intensity measured during deposition.

Numerical Study on the Influence of Tropical Cyclone Characteristics on the Sea State and Sea Surface Roughness inside the Tropical Cyclones

The development of wind wave (i.e., sea state) inside an intense tropical cyclone (TC) is the dominant contributor to the sea surface roughness and thus significantly impacts the air–sea interaction. The sea state is known to vary with TC characteristics (intensity, size, and translation speed); however, comprehensive knowledge of the influence of TC characteristics on the sea state and sea surface roughness is quite limited, largely because of the lack of observations. In this study, numerical experiments are performed to investigate the influence of TC characteristics on the sea state and the sea surface roughness under a range of idealized TCs. The numerical results indicate that the sea states are systematically younger for a more intense or smaller TC, and their azimuthal variation is predominantly determined by the TC translation. The dependence of the sea surface roughness on wind speed shows systematic variations with the TC characteristics, which are most significant for a moderately moving TC.

Unveiling the mystery of scale dependence of surface roughness of natural rock joints

Scale dependence of surface roughness of natural rock joints has long been an outstanding issue in rock mechanics. Controversial results were reported by various studies; however, the nature of scale dependency and the underlying mechanism for the conflicting observations remain unclear. Rock joints at different scales characterise two-order asperities, namely, waviness and unevenness; thus understanding how the individual roughness of waviness and unevenness vary as the joint size increases from the laboratory-scale to the large-scale is crucial for revealing the scale effect mystery. Here we digitise three natural granite joint surfaces with the same dimension of 1000 mm × 1000 mm through a high-resolution, three-dimensional scanner. Waviness and unevenness of each rock joint surface are quantitatively separated by selecting an appropriate sampling interval. The respective fractal dimensions of waviness and unevenness of joint surfaces sized from 100 mm × 100 mm to 1000 mm × 1000 mm are estimated through an improved roughness-length method. We find that the fractal dimensions of two-order roughness are scale-dependent but without generalised trends. The stationarity threshold beyond which the scale-dependency of roughness vanishes is absent for all the three joint samples, suggesting that the roughness of natural rock joints be assessed at the specific scale of the rock mass in-situ. We reveal that previous controversial results regarding scale effect are likely due to the composition of the roughness scaling of waviness and unevenness. Thus, accurate stability analysis of rock-engineering projects should consider separate contributions of multi-order asperities across scales to the strength and deformation of jointed rock masses.

Effects of deposition time on structural and optical properties of ZnS and ZnS/Au thin films grown by thermal evaporation

In this work, by exploiting the thermal evaporation technique, Zinc sulfide (ZnS) thin films are grown on glass substrates at 473 K. The effects of the deposition time on the thickness, structural, morphological, and optical properties of the thin films are investigated. The samples were deposited at 4 × 10−6 mbar with different deposition times (10, 20, and 30 min) whereas the thin films are characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), and ultraviolet–visible spectrophotometers (UV–Vis). XRD analysis indicates that all fabricated films have a cubic structure of β-ZnS phase. Moreover, crystallite size, lattice constant, dislocation density, and micro-strain are calculated from XRD data. According to the results, crystallite size shows an increasing trend from 7.05 to 12.28 nm as deposition time increases. The dependency of surface roughness on deposition time is also observed. Optical parameters of the films such as transmittance spectra, direct optical band gap energy, refractive index, extinction coefficient, complex dielectric constant, dispersion energy parameters, static refractive index, and static high-frequency dielectric constant are carefully determined. The films exhibit high transparency and zero absorption in the visible and infrared regions. The refractive index values can be well fitted to Cauchy's relations for extrapolation to near strong absorption region. The prepared ZnS thin film with low surface roughness, high transparency, and large optical band gap may find its application as optical interfacing and CIGS solar cells. Moreover, a thin layer of Au ∼20 nm was deposited by the thermal evaporation method on the prepared ZnS films and the optical transmittance spectra show that the bilayers possess a good transmittance ratio while the disappearance of spectral interference was observed as a result of Au deposition.

Abrasive machining of high-alloy corrosion resistant steels by example of 12Kh18N10T

The paper focuses on research into processing of high-alloy corrosion resistant steels by the method of centreless circular grinding. The physical and mechanical properties of such steels determine certain difficulties in their grinding as compared with other materials, which necessitates a thorough investigation of this issue. The paper presents experimental data on the dependence of machined surface roughness and hardness, as well as workpiece surface average temperature and microhardness, on the machining conditions and grinding wheel characteristics.

Sensitivity to changes in the surface‐layer turbulence parameterization for stable conditions in winter: A case study with a regional climate model over the Arctic

AbstractThe modeling of the atmospheric boundary layer over sea ice is still challenging because of the complex interaction between clouds, radiation and turbulence over the often inhomogeneous sea ice cover. There is still much uncertainty concerning sea ice roughness, near‐surface thermal stability and related processes, and their accurate parameterization. Here, a regional Arctic climate model forced by ERA‐Interim data was used to test the sensitivity of climate simulations to a modified surface flux parameterization for wintertime conditions over the Arctic. The reference parameterization as well as the modified one is based on Monin–Obukhov similarity theory, but different roughness lengths were prescribed and the stability dependence of the transfer coefficients for momentum, heat and moisture differed from each other. The modified parameterization accounts for the most comprehensive observations that are presently available over sea ice in the inner Arctic. Independent of the parameterization used, the model was able to reproduce the two observed dominant winter states with respect to cloud cover and longwave radiation. A stepwise use of the different parameterization assumptions showed that modifications of both surface roughness and stability dependence had a considerable impact on quantities such as air pressure, wind and near‐surface turbulent fluxes. However, the reduction of surface roughness to values agreeing with those observed during the Surface Heat Budget of the Arctic Ocean campaign led to an improvement in the western Arctic, while the modified stability parameterization had only a minor impact. The latter could be traced back to the model's underestimation of the strength of stability over sea ice. Future work should concentrate on possible reasons for this underestimation and on the question of generality of the results for other climate models.

Effects of oxygen concentration variation on the structural and optical properties of reactive sputtered WOx thin film

Tungsten oxide (WOx) has been widely investigated due to mainly its optoelectronic properties. This study primarily aimed to examine the influence of oxygen concentration on the structural and optical properties of WOx films. Herein, WOx thin films have been prepared by reactive sputtering method at low power (50 W) while controlling the Ar:O2 gas flow rate to vary oxygen concentration. Energy Dispersive X-ray (EDX) analysis reveals that the oxygen concentration depends on the gas flow rate. Such oxygen concentration changes affect the film’s thickness, confirmed by the field emission scanning electron microscope (FESEM). Atomic force microscopy (AFM) analysis ensures the dependency of surface roughness of the films on the oxygen concentration. The developed films exhibit the amorphous state as validated by X-ray Diffraction (XRD) analysis. The Ultraviolet–Visible (UV–Vis) spectroscopy measurement was also conducted to determine transmittance and absorbance of the film, which further allows realizing necessary optical parameters, such as absorption coefficient, skin depth, energy bandgap, refractive index, extinction coefficient, etc. The oxygen concentration-dependent optical parameters are investigated in the spectral range of UV to near-infrared regions to ensure the use of WOx for optoelectronic device applications. Finally, we considered the optimized WOx film as a potential electron transport layer (ETL) to realize an efficient perovskite solar cell. The optics and optimization of this solar cell were studied by finite-difference time-domain (FDTD) simulations. The investigation allows us to calculate the maximum quantum efficiency (QE) and short-circuit current density (JSC) of ~90% and 22.1 mA/cm2, respectively.

A comprehensive comparative study of the performance of carbon‐ and copper‐based interconnects in ultra‐large‐scale integrated circuits

AbstractContinuous increase of transistor count in ultra‐large‐scale integrated (ULSI) circuits demands denser interconnection networks to guarantee normal operation. As the distances between adjacent interconnect lines shrinks, severe crosstalk effects appear. New interconnect materials and technologies are proposed to alleviate deteriorating crosstalk effects and maintain overall circuit performance at a desirable level. Carbon‐based materials including carbon nanotubes (CNTs) and graphene nanoribbons (GNRs) are among promising candidate materials to replace copper in future ULSI interconnects. In this work, carbon‐based interconnects including multiwall carbon nanotubes (MWCNTs) and multilayer graphene nanoribbons (MLGNRs), both horizontal (HMLGNRs) and vertical (VMLGNRs), are compared with traditional copper interconnects in terms of crosstalk delay and noise. Due to lower surface roughness, boron nitride (BN) is considered as substrate material for carbon‐based interconnects. To obtain more accurate and reliable results, layer number dependence of dielectric constant of BN multilayers and surface roughness dependence of the resistivity of HMLGNR interconnects are considered. The role of interconnect length, line spacing, and interlayer distance (substrate thickness) in crosstalk delay and noise of coupled carbon‐ and Cu‐based interconnect lines is investigated. It is shown that VMLGNR interconnects with perfect GNR edges exhibit the least crosstalk delay while MWCNT interconnects show far less crosstalk noise than other materials.

ОСОБЕННОСТИ ОБРАБОТКИ ДЕТАЛЕЙ НЕФТЕГАЗОВОЙ ОТРАСЛИ, ВЫПОЛНЕННЫХ ИЗ ВОЛЬФРАМОВЫХ СПЛАВОВ

The purpose of the work carried out is to increase the effectiveness of hard alloy machining. Within the limits of the paper there is solved a matter of electro-erosion treatment and turning TC 3 alloy parts. Basic investigation methods are: - experiment and comparison, - computer simulation The work resulted in recommendations for the choice of cutters and cutting modes for hard alloy edge machining and also electrode material at electro-erosion treatment. One of the ways to increase productivity and operation quality equipment consists in the application of new materials and alloys including tungsten alloys. Within the limits of this work there are considered the peculiarities in machining TC3 alloy parts for oil-gas industry by the example of the “sleeve” part. For machining inner and outer surfaces there was used a turning operation, and for complex grooves – electro-erosion treatment as the only possible choice for processing because of a small size of the part. The peculiarities hard alloy machining through turning and basic reasons of hard alloy hard-to-workability are described. There are shown approaches to the choice of cutters, and the dependence of surface roughness and tool durability upon cutting mode choice is shown. During turning plate material must have higher strength than alloy under machining. One of the best choices for hard alloy machining is cubic boron nitride. For processing it is necessary to use tool holders with the increased rigidity. There are presented principles of electrode designing for hard alloy electro-erosion treatment and ways for process productivity increase. The application of copper-tungsten pseudo-alloys and m1 grade copper is compared from the point of view of economic purposefulness in their use. In spite of copper-tungsten alloy high durability which gives advantages in processing rate and economy in manufacturing electrodes its use is economically inexpedient and it is more rational to use copper which is cheaper.

Study on sputtering yield of tungsten with different particle sizes: Surface roughness dependence

The sputtering yield of tungsten pellets composed of different particle sizes of <1, 12, 44–74, and 149–297 μm was systematically investigated by bombardment with Ar+ ions accelerated at 2.0 keV in an ultra-high vacuum chamber. We found that the tungsten sample fabricated from larger particles had a higher surface roughness, based on the surface profile results. Using the data of the surface roughness for the four types of tungsten pellets, we confirmed that the sputtering yield for a tungsten pellet with the highest surface roughness was 7 times lower than that of the lowest surface roughness. This could be due to the redeposition of sputtered tungsten particles onto neighboring asperities.

Mapping the growth of p-type GaN layer under Ga-rich and N-rich conditions at low to high temperatures by plasma-assisted molecular beam epitaxy

We present a detailed study of Mg acceptor, p-type doping of GaN grown by plasma-assisted molecular beam epitaxy in both Ga-rich and N-rich conditions at low (∼580 °C) to high growth temperatures (∼740 °C). A growth map is constructed using results from a broad range of growth conditions, which shows the dependence of Mg incorporation and surface roughness on the III/V ratio and growth temperatures. Detailed secondary ion mass spectroscopy and atomic force microscopy studies confirmed that N-rich conditions are favorable for significantly higher Mg-incorporation efficiency (∼80%), whereas the Ga-rich growth condition is preferable for achieving a smooth surface morphology (root mean square roughness: ∼1–2 nm) with poor Mg incorporation. The room temperature Hall measurement confirms that the hole concentration in the range of ∼7 × 1017 to 2 × 1019 cm−3 can be achieved in Ga-rich and N-rich conditions, respectively, at a fixed Mg flux depending on the growth conditions. Our detailed study provides a proper guideline for realizing an efficient Mg-doped GaN layer and is applicable, in principle, to different nitride-based electronic and photonic devices.

On the Wave State Dependence of the Sea Surface Roughness at Moderate Wind Speeds under Mixed Wave Conditions

AbstractWind stress depends on the sea surface roughness, which can be significantly changed by surface wind waves. Based on observations from a fixed platform, we examined the dependences of the sea surface roughness length on dominant wave characteristic parameters (wave age, wave steepness) at moderate wind speeds and under mixed-wave conditions. No obvious trend was found in the wave steepness dependence of sea surface roughness, but a wave steepness threshold behavior was readily identified in the wave age dependence of sea surface roughness. The influence of dominant wind waves on the surface roughness was illustrated using a wind–wave coupling model. The wave steepness threshold behavior is assumed to be related to the onset of dominant wave breaking. The important role of the interaction between swell and wind wave was highlighted, as swell can absorb energy from locally generated wind wave, which subsequently reduces the wave steepness and the probability of dominant wave breaking.

Optical and Structural characterization of spraying ZrO2 and doped B: ZrO2 thin films

Zirconium oxide (ZrO2) and doped with boron (B) thin films were prepared by Chemical spray pyrolysis CSP. Optical band gap energy of the films decreased from 3.83 to 3.73.55 eV via increase of doping. X-XRD patterns disclosed that films structure were polycrystalline, mixture of monoclinic and tetragonal phases. Atomic force microscopy (AFM) results assure dependence of surface morphology and roughness upon doping.

Improving the facade element surface processing of MDF case furniture

A lot of enterprises engaged in the production of MDF case furniture face the problem of milled plate surface quality. It ensures the production of facing paper and synthetic film or finishing liquid paints and varnishes to improve the facade element surface processing quality of MDF case furniture. The experiments to study the roughness of MDF plates milled surface have been carried out, depending on the feed rate and tool rotation frequency. The work has been carried out using hard-face end mill tools manufactured in accordance with the patent for the utility model (Russian Federation), which enables to improve the quality of machined surfaces by performing finishing milling in one pass and increasing equipment productivity. The determination of the roughness parameter has been carried out in accordance with the requirements of 15612 State Standard. As a result of experimental processing, the dependences of milled surface roughness on the factors under study in the form of regression equations have been obtained. The mathematical dependencies are the results of this work. It enables to set regime parameters for profile milling of MDF surface plates to obtain the required roughness. The optimal milling mode has been determined improving surface finish facade element quality of MDF case furniture.