Surface Roughness Distribution Research Articles

Optimizing Melamine Sponges Modified With Titanium Dioxide Nanoparticles for Environmental and Industrial Applications

ABSTRACTThis study explored the development and characterizations of a lightweight, cost‐effective, and easily accessible titanium dioxide (TiO2)/melamine sponge with outstanding hydrophobicity, oil absorption/separation, flame retardancy, durability, and electromagnetic wave absorption capacities. Commercial melamine sponges were modified using the silane coupling agent and TiO2 nanoparticles via a solution‐immersion method. Scanning Electron Microscopy revealed the structural integrity and surface morphology with increased surface roughness and uniform distribution of TiO2 particles. The hydrophobicity of the TiO2/sponge was confirmed by contact angle measurements, showing a high value of 145°. The oil absorption capacity and separation efficiency were also quantified, with the modified sponges able to absorb oils at 70 to 120 times their weight while maintaining a separation efficiency above 95% even after 10 reuse cycles. Additionally, the TiO2/sponge exhibited excellent flame resistance, strong mechanical abrasion resistance, and stability in saline environments. Electromagnetic absorption tests over the 2–18 GHz range showed efficient absorption, with reflection loss values below −10 dB at higher frequencies for thicker sponges. These results suggest that TiO2/sponge composites provide multifaceted enhancements, making them suitable for various environmental and industrial applications, including oil spill management and electromagnetic radiation mitigation.

An Experimental Study on the Effect of Nano Zinc Oxide on Reflective Coatings and Building Roof Temperatures

Most roofs on Earth are made of dark materials. Dark roof surfaces can retain heat better than light ones; in Iraq, summer time temperatures on the roofs of dark buildings reached 70–80 degrees Celsius in July and August. The effects of this temperature rise are detrimental to cooling and energy consumption. To lessen heat transfer into the building, use reflective surfaces that can reflect infrared radiation waves. Cool roofs have both short-term and long-term advantages. They can reduce a building's annual air conditioning energy consumption by up to 15%, extend the life of the roof and its service life, improve the energy efficiency of roofs particularly those with inadequate insulation at the front of the roof improve thermal comfort in buildings without air conditioning, and lower greenhouse gas emissions and air pollution. Solar heat is one of the main factors affecting the durability of roofing membranes, according to research and real-world experience with the deterioration of these materials over time. High solar reflectance materials can reflect more sunlight and maintain their coolness in the sun. This study examines a low-cost composite cool coating that uses 60% calcium carbonate and demonstrates a 15°C drop in surface concrete temperature for roof buildings when compared to an uncoated surface. Additionally, compared to 30%wt CaCO3, the effect of 60%CaCO3 in composite coating reduces adhesion strength. According to the study, the weight of CaCO3 in the composite coating increases while adhesion strength, surface roughness, and particle homogeneity distribution decrease. Conversely, the maximum weight of CaCO360% weight percent exhibits good IR reflectance and less tribological properties. While preserving good infrared reflectance, adding 10% ZnO to the coating solution (60% CaCO3/PVac) improves tribological properties. The adhesion strength of the 60% calcium carbonate polymer composite paint increased from 10.9 MPa to 40.2 MPa when the nanomaterial was present, while this material maintained the superior optical qualities of infrared reflection. The coefficient of thermal expansion varies between concrete and coating solutions. For instance, the coating that has 10% weight added ZnO has a peel resistance coefficient of 8*10-6 1/K. The 60%CaCO3/10%ZnO/PVac coating effectively lowers the temperature by 15–12 °C when applied to a building roof.

Effects of Homogeneous and Inhomogeneous Roughness on the Ship Resistance

Ship hull roughness can significantly increase the ship resistance. The roughness caused by biofouling attached to the ship hull is not uniform but has a random distribution. The purpose of this study is to investigate how the inhomogeneous surface roughness distribution affects the ship resistance and the various resistance components. The KRISO container ship (KCS) is considered as a case study. To model the inhomogeneous surface roughness, the ship hull is divided into three segments with equal wetted surface area. Combinations of three roughness heights, denoted as P, Q, and R with ks values of 125 μm, 269 μm, and 425 μm, respectively, are considered to obtain homogeneous and inhomogeneous roughness arrangements (PPP, QQQ, RRR, PQR, PRQ, QPR, QRP, RPQ, and RQP). CFD method is utilized in this study, utilizing RANS equations and k-ω SST turbulence model. A VoF method is used to model the free surface. CFD simulation results show that for the homogeneous roughness, the total resistance coefficient CT increases with increasing ks (PPP < QQQ < RRR), as expected. For the inhomogeneous roughness, the friction resistance coefficient CF increases in the order PQR < PRQ < QPR < QRP < RPQ < RQP, consistent with results from earlier studies. In all the cases, the friction resistance (CF) is the dominant component of the total resistance. As Re increases from 2.2 x 109 to 2.7 x 109, the percentage of the friction resistance decreases, while the percentage of the wave resistance increases. The viscous-pressure resistance decreases slightly as Re increases from 2.2 x 109 to 2.7 x 109.

Surface Roughness Evaluation of Blast-Cleaned Structural Steel Plates Considering Measurement Deviation

Surface roughness is an important characteristic of blast-cleaned structural steel plates. This is because the adhesion of the coating and the frictional grip of the bolted connections are related to surface roughness. Surface roughness is usually measured using a surface roughness meter. Because the roughness of blast-cleaned surfaces is not uniform, it varies from position to position. The surface roughness test results obtained from a broad area are more valuable than those obtained from a narrow area. Because the measured values contain deviations, they are measured multiple times and averaged to reduce the influence of deviations. However, to evaluate roughness, it is necessary to clarify the measurement conditions to obtain accurate results. Consider combining these sentences as follows: In this study, the surface roughness of the blast-cleaned structural steel sample was measured at multiple locations to obtain its distribution characteristics. During each sample measurement, the detection sensor of the surface roughness meter was lifted and placed on the steel sample to determine deviations from the actual results. The surface roughness distributions of five blast-cleaned samples were the same under the identical measurement conditions. This indicates that accurate results can be obtained by measuring representative samples, without the need for measuring all samples; actually, 17 measurements were adequate to obtain a mean surface roughness value with a 95% confidence level and a 5% acceptable error rate.

Quantification of immiscible displacement in a rough-walled fracture through direct visualization

Subsurface substance migration in the fractured rock aquifer is mainly controlled by fractures, and immiscible fluid-fluid displacement in fractures is important to many geophysical processes and engineering activities. Using a fracture-visualization system, we present the qualitative and quantitative assessment of fracture geometry associated with fluid movement and distribution in the rough fracture. Based on fracture geometry and statistical analysis, we first conducted a quantitative study of fracture surface roughness and aperture distribution. Then, fractal dimensions of displacement front and residual oil distribution were determined by image processing procedures. Influenced by wettability and micro-scale roughness, at the end of the displacement, residual oil saturation of molded sample is lower (6.45%–25.74%), and displacement pattern is more uniform, indicating that displacement effect is better. Due to smaller differences in residual oil saturation (9.08%) under different injection directions, the impact of wettability on the displacement process is greater than that of anisotropic roughness. Additionally, the fractal dimension of the displacement front increased under low injection rates initially but decreased when the rate was increased later. Overall, visualized temporal monitoring of experimental images enabled us to provide a preliminary assessment of the impact of anisotropic roughness and the material constituting the fracture wall on invading fluid saturation and the fractal dimension of the displacement front under various injection rates.

Functional insights into the interaction of Lactobacillus spp. and potentially protective agents

The research addresses the critical need to explore how potentially protective agents (PPAs) influence the cellular characteristics of probiotic bacteria, with a focus on strain-specific responses. This study aimed to reveal the effect of 48-h exposure of the Lactobacillus spp. strains to selected PPAs on the viability, metabolic activity, stress response, surface properties, and physicochemical stability of bacterial suspensions. Results provide new insights into the potential risks or benefits of using the tested PPAs in probiotic production based on the analyzed strains, offering valuable information on their impacts on bacterial cells. Trehalose (TRE) and vitamin C (VC) notably impact the metabolic activity and surface characteristics of cells, with TRE improving viability and VC changing surface roughness and particle size distribution (PSD), suggesting a delicate balance between stress induction and viability enhancement. Inulin (IN) decreased metabolic changes, pointing the complex interplay between PPAs and bacterial metabolism. Results of zeta potential and PSD measurements revealed that other PPAs can either promote uniformity or induce aggregation of the bacterial suspensions. Findings have shown significant strain-specific effects of PPAs on bacterial viability and functionality, suggesting that their careful selection can improve bacterial health. Future directions include exploring the molecular mechanisms behind PPAs' effects and their practical applicability in real food systems.

When and Where Lithium Plating Occurs, Its Correlation with Microstructure Heterogeneity, and the Mechanisms That Initiate and Self-Regulate Electrochemical Heterogeneity

A microstructure scale electrochemical LIB model was used to investigate lithium plating onset, material non-uniform utilization, and in-plane heterogeneities for an NMC-graphite full cell [1]. Model predicts active material particle surface roughness and size distribution (respectively, non-uniform curvature within and between particles) initiate in-plane heterogeneity, and that particle size heterogeneity at the separator interface controls the lithium plating preferential deposition (“Where”). These in-plane heterogeneities are then exacerbated by through-plane heterogeneities induced at fast charge as electrolyte depletion occurs and concentrates intercalation reaction near the anode-separator interface. Also, overall magnitude and occurrence of lithium plating is controlled by effective, or macroscale, microstructure parameters (“When”).As local states of charge start to diverge between nearby active material regions, overpotential differences induced by OCP difference kick in and contribute to reduce these SOC local heterogeneities. However, for staged materials such as graphite, with OCP profile alternating between plateaus and varying regions, this balancing mechanism is, respectively, inactive and active. This leads to a dynamic, non-monotonic, in-plane heterogeneity time evolution for state of charge and Faraday current density, for which their respective in-plane heterogeneity magnitude alternates. Such behavior has been modeled both for the whole electrode at the microstructure scale and at the particle scale. In-plane heterogeneities are usually considered to be detrimental, as they result in material non-uniform utilization (i.e., under and over stressed regions) and earlier degradations. However, this work provides a more granular approach as it discriminates between a harmful in-plane heterogeneity (non-uniform curvature) that triggers SOC in-plane heterogeneity, and a beneficial in-plane heterogeneity (Faraday current density) that contributes to reduce SOC in-plane heterogeneity.This work comprehensively explains the mechanisms that initiate, exacerbate, and regulate heterogeneity at the microstructure scale, while providing some design suggestions to reduce both in-plane and through-plane heterogeneities, as summarized in the graphical abstract.[1] F. L. E. Usseglio-Viretta, A. M. Colclasure, J. Allen, D. P. Finegan, P. Graf, and K. Smith, Microstructure Scale Lithium-ion Battery Modeling, Part I: on lithium plating prediction and heterogeneity, in preparation. Figure 1

Estimating Residual Oil Saturation in Carbonate Rocks: A Combined Approach of Direct Simulation and Data-Driven Analysis

Summary Estimating residual oil saturation (Sor) post-waterflooding is critical for selecting enhanced oil recovery strategies, further field development, and production prediction. We established a data-driven workflow for evaluating Sor in carbonate samples using microcomputed tomography (μ-CT) images. The two-phase lattice Boltzmann method (LBM) facilitated the flooding simulation on 7,192 μ-CT samples. Petrophysical parameters (features) obtained from pore network modeling (PNM) and feature extraction from μ-CT images were utilized to develop tree-based regression models for predicting Sor. Petrophysical features include porosity, absolute permeability, initial water saturation (Swi), pore size distribution (PSD), throat size distributions (TSD), and surface roughness (Ra) distribution. Our method excludes vugs and macro/nanoporosity, which complicates multiscale simulations—a recognized challenge in modeling carbonate rocks. When subdividing the image into numerous subvolumes, certain subvolumes may contain vugs exceeding the dimensions of the subvolume itself. Hence, these vugs were omitted given the entirety of the image constitutes a vug. Conversely, vugs with dimensions smaller than those of the subvolume were not excluded. Despite scale limitations, our subsampling, supported by substantial data volume, ensures our microscale porosity predictions are statistically reliable, setting a foundation for future studies on vugs and nanoporosity’s impact on simulations. The results show that features obtained from dry-sample images can be used for data-driven Sor prediction. We tested three regression models: gradient boosting (GB), random forest (RF), and extreme gradient boosting (XGBoost). Among these, the optimized GB-based model demonstrated the highest predictive capacity for Sor prediction [R2 = 0.87, mean absolute error (MAE) = 1.87%, mean squared error (MSE) = 0.12%]. Increasing the data set size is anticipated to enhance the models’ ability to capture a broader spectrum of rock properties, thereby improving their prediction accuracy. The proposed predictive modeling framework for estimating Sor in heterogeneous carbonate formations aims to supplement conventional coreflooding tests or serve as a tool for rapid Sor evaluation of the reservoir.

Optimizing sheet metal edge quality with laser-polishing: surface characterization and performance evaluation

Dual-phase (DP) steels are widely used in the automotive industry due to their exceptional performance. It offers excellent strength, ductility, formability, and weldability. However, there is a high risk of edge cracking, particularly in materials like DP1000 steel, caused by residual damage from blanking, such as microcracks and burrs, which needs further investigation. In this study, the transformative potential of laser-polishing on DP1000 steel was investigated. The goal was to reduce edge crack sensitivity and enhance edge formability. In this work, laser-polished samples produced by various pre-manufacturing techniques such as sawing, punching, and waterjet cutting were examined. Various evaluations were performed on laser-polished samples. Those included white-light-confocal microscopy, scanning electron microscopy, and Electron Backscatter Diffraction (EBSD) analysis. Those evaluations aimed to analyze the microstructural transformation, surface roughness, and micro grain size distribution resulting from laser-polishing. Laser-polishing is a process in which the edge of the sample is remelted locally. Hence, residual damage vanishes, and surface defects disappear, which should be beneficial for edge formability. On the other hand, the cooling rate during re-solidification is high, leading to high strength and reduced ductility compared to the initial DP steel. Therefore, hole expansion tests were conducted to evaluate the edge formability of the steel. The results indicated a significant improvement in the hole expansion ratio of the laser-polished samples compared to samples with conventional manufactured edges. These findings will help to assess the advantages and limitations of laser-polishing in sheet material manufacturing.

Analysis of Subsurface Damage Structures of Gallium Nitride Substrates Induced by Mechanical Polishing with Diamond Abrasives

Subsurface damage (SSD) structures induced by mechanical polishing of gallium nitride (GaN) substrates are comprehensively investigated using atomic force microscopy, cathodoluminescence (CL) imaging, and cross‐sectional transmittance electron microscopy. The low removal rate of the CMP process is a barrier to high productivity of a GaN wafering process; therefore, reducing the chemical mechanical polishing (CMP) process time by reducing the depth of SSD induced by mechanical processing is an active research area. To better understand the SSD structures, the surface roughness, SSD depth, and SSD distributions induced by mechanical polishing are quantitatively evaluated in this study. The SSD structures induced by mechanical polishing can be quantitatively exhibited as the SSD distribution with the damage strength at the outermost surface and the damage propagation, which are obtained by CMP process time‐resolved CL imaging method. On the basis of the analysis results, a schematic model of the SSD structures for mechanically polished GaN substrates is proposed.

Universal simulation of absorption effects for X-ray diffraction in reflection geometry.

Analytical calculations of absorption corrections for X-ray powder diffraction experiments on non-ideal samples with surface roughness, porosity or absorption contrasts from multiple phases require complex mathematical models to represent their material distribution. In a computational approach to this problem, a practicable ray-tracing algorithm is formulated which is capable of simulating angle-dependent absorption corrections in reflection geometry for any given rasterized sample model. Single or multiphase systems with arbitrary surface roughness, porosity and spatial distribution of the phases in any combination can be modeled on a voxel grid by assigning respective values to each voxel. The absorption corrections are calculated by tracing the attenuation of X-rays along their individual paths via a modified shear-warp algorithm. The algorithm is presented in detail and the results of simulated absorption corrections on samples with various surface modulations are discussed in the context of published experimental results.

Effects ofAs8structure formation on the surface morphology and internal microstructure of GaAs thin films.

Gallium arsenide (GaAs) materials have the advantages of high electron mobility, electron saturation drift rate, and other irreplaceable semiconducting properties. They play an important role in the electronics, solar and other fields. However, during GaAs film sedimentary growth, As atoms can undergo segregation to formAs8clusters because of the influence of external factors, which affect the surface morphology and internal structure of these films. In this study, a series of investigations on the deposition and growth of GaAs crystal films were performed. Additionally, the deposition and growth of GaAs thin films were simulated using molecular dynamics. The influence of As8clusters on the surface morphology and internal structure of GaAs films at different incidence angles, velocities and substrate temperatures was studied by using 'defect analysis technology' and 'diamond structure identification' in open source software, along with surface roughness and radial distribution function. Results show that with increasing incident angle, the number ofAs8clusters decreases and film density increases. Increasing incident velocity increases the irregular movement ofAs8clusters in air, and their deposition on the film surface affects the morphology of the film, and the surface roughness increases first and then decreases. Additionally, we investigated the effect of different substrate temperatures on the film surface. Results show that at a substrate temperature of 1173 K, the number ofAs8clusters in the film decreases or the As8clusters disappear, heterogeneous nucleation occurs in the film, and the crystallization rate increases. Although the dislocation line associated with nucleation may affect the mechanical and optical properties of the film, it considerably reduces the annealing effort after the deposition and growth.

Rates of air flow in and out of closed atmospheric-pressure plasma jet system affected surface properties of treated polysulfone membrane

The cold plasma jet works in an atmospheric-pressure condition, and is used to modify polymer membranes by creating hydrophilic functional groups on the membrane surface. Since it can be used without a pressure-reducing system, treatment time and cost are reduced. However, the plasma jet has a narrow beam which limits the area of the membrane surface that can be activated. In this study, a plasma jet was generated in a closed system with controllable rates of air flow in and out of the system. The plasma discharge was recorded with a camera and analyzed by optical emission spectroscopy (OES). Polysulfone membrane surfaces were treated with various conditions of plasma discharge, and the induced membrane hydrophilicity was assessed from water contact angle (WCA) and surface energy (SE) measurements. Atomic force microscopy (AFM), Fourier Transform Infrared Spectroscopy (FTIR) and WCA contour mapping were respectively employed to study surface roughness, functional groups, and WCA distribution on the treated membrane surfaces. The airflow had distinctly different effects on the plasma characteristics. The inflow rate condition affected the width of the plasma beam, and the outflow rate condition affected the diffusion of the plasma beam. Water flux was changed according to the plasma characteristic, and an air outflow rate of 6 L/min was the optimum condition for this experiment.

A novel equivalent model of radionuclide migration in three-dimensional rough shear fractures

Accurate prediction of radionuclide distribution in fractured rock mass is a key problem in high-level radioactive waste disposal engineering. However, it is inappropriate to directly regard rough fractures as smooth fractures when predicting radionuclide migration in real fractured rock masses. In this study, the characteristics of radionuclide migration in three-dimensional rough shear fractures are numerically analyzed considering the influence of fracture roughness, aperture distribution, contact ratios, and adsorption. Different fracture contact ratios and aperture distributions are realized by shearing two rough fracture surfaces. Based on the study, we found that the influence of surface contact is greater than that of surface roughness and aperture distribution on radionuclide migration in rough fractures with the same initial fracture aperture under laminar flow. The phenomena of dominant migration channels and low-velocity dispersion zones are observed for radionuclide dispersion in rough fractures containing contact areas. The higher the contact ratio, the more obvious this phenomenon. The breakthrough and steady state times of radionuclide are also significantly affected by the contact ratio. The higher the contact ratio, the shorter the breakthrough time, and the longer the duration from the breakthrough time to the steady state time. Adsorption delays the overall process of the radionuclide migration and prolongs the duration between the breakthrough time and the steady state time. A novel equivalent method of the radionuclide migration in rough shear fractures is proposed based on the study of radionuclide transport in rough fractures. In the proposed equivalent method, an adjustment coefficient for the transport velocity and a longitudinal dispersion coefficient for the rough fracture are defined to connect rough fractures and the corresponding smooth fractures with the same fracture aperture. The influence regularity of fracture contact and adsorption on the two defined coefficients is obtained based on over 400 numerical simulations. The specific formulas of the two coefficients are given based on the form of the analytical solution for the radionuclide transport in a smooth fracture. The dispersion coefficient and transport velocity in a rough fracture are equivalent to the dispersion coefficient and transport velocity in a smooth fracture and the fluctuation term affected by fracture surface contact and adsorption, respectively. It was verified that the equivalent model has higher accuracy, which can help characterize radionuclide migration in 3D rough fractures efficiently and precisely.

Effect of Electrospinning Parameters on the Morphological and Thermal Properties of ABS/ENR Electrospun Fibres

The electrospun of the Acrylonitrile-butadiene-styrene (ABS) blend with epoxidized natural rubber (ENR) is fabricated using the electrospinning technique. Research shows that ABS/ENR electrospun fibres have not been studied. The effects of electrospinning parameters were investigated to determine a significant effect on the microstructure, surface roughness, fibre diameter, and fibre distribution of the electrospun membranes. Sample preparation is made straightforwardly by dissolving ABS and ENR in acetone solvent using a magnetic stirrer. In this research, there are two solution parameters being studied: the ABS/ENR solution concentration (15 to 25 wt.%) and the ratio of ENR (100:0, 70:30, 50:50). Meanwhile, process parameters that are being studied are applied voltage (15 kV to 30 kV) and distance from syringe tip to collector (5cm to 15cm). FTIR results showed that hydrogen bond interaction occurs between ABS and ENR. According to the SEM images, micrometre and sub-micrometre fibres with a smooth surface and bead formation were produced at a concentration of 25%, a ratio of 70:30, a voltage of 30kV, and a distance of 15cm. The diameter of electrospun fibres increases with increasing solution concentration, ranging from 400 nm to 4.5 µm. The diameter of the electrospun fibres decreased with the addition of ENR, increasing voltage, and tip-to-collector distance. TGA results showed that ABS/ENR blends gave higher degradation temperature (393.7°C) than pure ABS (368.8°C), which enhanced thermal stability.

Effects of surface morphology on the performance of water-lubricated thrust bearings

Purpose As the crucial support component of the propeller power system, the reliability of the operation of submersible pumps is influenced by the lubrication performance of water-lubricated thrust bearings. When the water-lubricated thrust bearings are under start-stop or heavy load conditions, the effect of surface morphology is crucial as the mixed lubrication regime is encountered. This paper aims to develop one mixed lubrication model for the water-lubricated thrust bearings to predict the effects of surface skewness, kurtosis and roughness orientation on the loading carrying capacity and tribological behavior. Design/methodology/approach This paper developed one improved mixed lubrication model specifically for the water-lubricated thrust bearing system. In this model, the hydrodynamic model was improved by using the height of the rough surface and its probability density function, combined with the average flow model. The asperity contact model was improved by using the equation for the Pearson system of frequency curves to characterize the non-Gaussian aspect of surface roughness distribution. Findings According to the results, negative skewness, large kurtosis and lateral surface pattern can improve the tribological performance of water-lubricated thrust bearings. Optimizing the surface morphology is a reasonable design method that can improve the performance of water-lubricated thrust bearings. Originality/value In this paper, one mixed lubrication model specifically for the water-lubricated thrust bearing with the effect of surface roughness into consideration was developed. Based on the developed model, the effect of surface morphology on tribological behavior can be evaluated. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2023-0247/

Waste Coffee Ground-Derived Porous Carbon for Neurochemical Detection.

We present an optimized synthetic method for repurposing coffee waste to create controllable, uniform porous carbon frameworks for biosensor applications to enhance neurotransmitter detection with fast-scan cyclic voltammetry. Harnessing porous carbon structures from biowastes is a common practice for low-cost energy storage applications; however, repurposing biowastes for biosensing applications has not been explored. Waste coffee ground-derived porous carbon was synthesized by chemical activation to form multivoid, hierarchical porous carbon, and this synthesis was specifically optimized for porous uniformity and electrochemical detection. These materials, when modified on carbon-fiber microelectrodes, exhibited high surface roughness and pore distribution, which contributed to significant improvements in electrochemical reversibility and oxidative current for dopamine (3.5 ± 0.4-fold) and other neurochemicals. Capacitive current increases were small, showing evidence of small increases in electroactive surface area. Local trapping of dopamine within the pores led to improved electrochemical reversibility and frequency-independent behavior. Overall, we demonstrate an optimized biowaste-derived porous carbon synthesis for neurotransmitter detection for the first time and show material utility for viable neurotransmitter detection within a tissue matrix. This work supports the notion that controlled surface nanogeometries play a key role in electrochemical detection.

Experimental investigation on the effect of grain size of granitic rocks on the fracture roughness and toughness

The fracture surface characterization, such as the fracture roughness, is essential to flow and heat transport through the fracture in the geothermal, oil, and gas reservoirs stimulation by hydraulic fracturing. This research presents an experimental approach to assess the correlation between the fracture roughness and mode I fracture toughness (KIc) of the granitic rock with different grain sizes, which is crucial in geothermal reservoirs. Three types of granite with the same mineralogical compositions but fine, medium, and coarse-grained structures were selected and prepared. Fracture toughness values were measured using a novel specimen called ENDB (Edge Notched Disc Bend), in which a cracked disc shape specimen was loaded in three-point bending. The photogrammetric method was used to estimate the value and distribution of surface roughness after ENDB testing and investigate the relationship between fracture morphology and fracture toughness. Based on the experiments, a clear correlation between the roughness and fracture toughness was observed in the three investigated granite types with different grain sizes. The FPZ around the crack tip, tortuosity, intergranular, and transgranular cracks were examined to study the effect of grain size on fracture toughness and roughness precisely. The results show that by increasing the grain size, KIc and surface roughness increased. The results also showed that the roughness parameter for the three types of rocks in the direction of the crack growth path is greater than the direction perpendicular to the crack growth path.

Experimental Study on the Influence of Surfactants on Ore Surface Wettability.

To reveal the evolution law of ore surface wettability under the condition of adding surfactant and chemical reaction, the test experiments of ore surface morphology, roughness, and chemical element distribution were carried out. The results show that the contour of the ore surface morphology was relatively flat in the early stage of leaching and the roughness factor increased slowly, while the contour fluctuated significantly in the late stage of leaching and the roughness factor increased sharply. With the leaching reaction, the roughness factor and spreading coefficient of the ore with a 0.008 mol/L surfactant (sodium dodecyl sulfate) concentration were always higher than those without surfactant and the surfactant enhanced the erosion effect of the solution on the ore surface. During the leaching process, the chemical elements Cu, Al, and K were dissolved on the ore surface, and the content of Cu decreased significantly from 2.01 to 0.86%; the leaching rate of copper was about 57.2%. According to the morphology characteristics of the ore surface during leaching and the distribution law of chemical elements on the ore surface before and after leaching, the leaching process was divided into four stages of "contact-penetration-reaction-disintegration". The surfactant had the most obvious effect on the ore surface morphology in the two stages of "reaction" and "disintegration".

Analysis of the influence of electrospark alloying parameters on the structural state of alloyed surfaces

Рroblem. Among the promising methods of surface hardening and modification are techniques based on the treatment of metals and alloys with high-energy flows of materials and energy. Among the modern methods of metal surface treatment is electrospark alloying (ESA), which allows obtaining surface structures with unique physical, mechanical and tribological characteristics. It is known that alitization provides metal surface layers with protection against corrosion and oxidation at elevated temperatures. The traditional method of forming alitized coatings is chemical-thermal treatment. The paper proposes a method of alitization by ESA. Many parameters influence the formation of the layer during alitization by the ESA method. First of all, it is the energy parameters. Goal. The aim of the work is to evaluate the effect of the ESA alloying process performance on the structure formation. Methodology. The study was carried out on samples of steel 20. An aluminium electrode in the form of a wire was used as a tool electrode for ESA. Different alloying modes were investigated, the discharge energy and performance were changed. The alloying was carried out in two stages. At the first stage, the aluminium electrode was used at classical performance values. At the second stage, the capacity was reduced by two and four times. At the second stage, a saturating paste containing aluminium powder was applied to the surface before the ESA. The microstructure of the obtained modified surfaces was examined under an optical microscope, the surface roughness and microhardness distribution in the surface layer were determined. Results. The use of two-stage alitization increases the microhardness of the hardened layer and the diffusion zone, as well as reduces the surface roughness. The coating integrity was 100%. (originality) A new method of alitisation based on ESA is proposed, which allows to obtain 100% continuity with high adhesion to the substrate. Рractical value. For practical implementation, it is recommended to perform alitization according to the following variant: the first stage is ESA with an aluminium electrode with a discharge energy Wp = 4.6-6.8 J, the second stage is the application of a saturation paste containing aluminium powder and graphite powder. Electrospark alloying should be carried out with a reduced productivity by about two times.