Increment Of Roughness Research Articles

Fractographic Analysis of Tensile Failures of Zirconia Epoxy Nanocomposites

This work characterizes the fractographic features of the neat epoxy and ZrO2 epoxy nanocomposites. All samples were subjected to a tensile test to determine the tensile strength and tensile modulus. SEM images were used to study the morphology of the fractured surface. The fractographic of the fracture surfaces were studied by microstructure analysis program (j-images) to specify the effect of ZrO2 nanoparticles on tensile performance and failure mechanism for ZrO2 epoxy nanocomposites. The tensile test results show that the addition of ZrO2 nanoparticles (2, 4, 6, 8, and 10 vol.%) to the epoxy matrix leads to increase the tensile strength about 40% for optimal content of ZrO2 nanoparticles at 4 vol.%, tensile modules of ZrO2 epoxy nanocomposites increased about 200% for optimal content of ZrO2 nanoparticles at 4 vol.%. SEM images show that the patterns of fractured surfaces of ZrO2 epoxy nanocomposites are different from the pattern of the neat epoxy. The fracture roughness of ZrO2 epoxy nanocomposites increased with the increases of the percentages of ZrO2 nanoparticles, where the increment of fracture roughness about 30% for optimal content of ZrO2 nanoparticles at 4 vol.% can be indicator for the improvement of mechanical properties (tensile strength and modules).

A Fractal Model for Effective Thermal Conductivity in Complex Geothermal Media

Thermal conductivity is an important macroscopic thermo-physical parameter due to its significant effects on the temperature field distribution and heat flow magnitude in the material at heat conduction equilibrium. However, because of the extremely complex pore structure and disordered pore distribution, a well-accepted relationship between effective thermal conductivity (ETC) and geometric structural parameters is still lack. In this study, a novel fractal model with variation pore diameter is established systematically based on the assumption that the rough elements of wall surface, pore size distribution and capillary tortuosity follow the fractal scaling law. Thermal-electrical analogy is introduced to predict the ETC of unsaturated geothermal media. The proposed model explicitly relates the ETC to the microstructural parameters (relative roughness, porosity, fractal dimensions and radius fluctuation amplitude) and fluid properties. The proposed model is validated by comparing with existing experimental data. A parametric analysis is performed for presenting the effects of the structural parameters and fluid properties on the ETC. The results show that pore structure has significant effect on ETC of unsaturated porous media. ETC gradually decreases with the increment of porosity, relative roughness, and fractal dimensions. The present study improves the accuracy in predicting ETC and sheds light on the heat transfer mechanisms of geothermal media.

Degradability of bulk-fill resin composites after cyclic immersion in different distilled alcoholic beverages.

To investigate effect of distilled alcoholic beverages on surface hardness, roughness, and erosion of bulk-fill resin composites. Sixty eight specimens of each bulk-fill resin composite (Filtek One Bulk Fill Restorative, SonicFill 2, and Tetric N-Ceram Bulk Fill) were prepared. Baseline data of surface hardness and roughness value were recorded. The specimens were divided into five groups: vodka, whisky, tequila, brandy, and deionized water (served as a control). Specimens were then alternately immersed in 25 ml of a storage agent for 5s and in 25 ml of artificial saliva for 5s over 10cycles. This process was repeated for 14 days. After immersion, specimens were subjected to evaluation of surface hardness, roughness, and erosion on days 7 and 14. The data were statistically analyzed by two-way repeated analysis of variance, Tukey's honestly significant difference, and a t test (p < 0.05). Distilled alcoholic beverages caused significant hardness decrement, roughness and erosion increment (p < 0.05), where the greatest degradation was found in brandy group. Tetric N-Ceram Bulk Fill had the most significant decrement in hardness and increment in roughness and erosion than the other resin composites (p < 0.05). Distilled alcoholic beverages affected hardness, roughness, and erosion of all the bulk-fill resin composites. Regarding the bulk-fill resin composites tested, Filtek One Bulk Fill Restorative was the most appropriate restorative material in patients who consume distilled alcoholic beverages.

Enhancement of laser heating process by laser surface modification on Titanium alloy

Titanium alloys are widely utilized in laser heating applications. However, it has poor optical properties due to low laser energy absorption. Nevertheless, a higher energy absorption can be realized by modifying the surface profile through increasing the surface roughness. In this present work, the laser surface modification (LSM) process was carried out to increase the roughness on surface of Ti6Al4V titanium alloy. Subsequently, the surface characterization and surface roughness were analysed by using the 3D optical microscope. The effect of laser power on the increment of surface roughness was investigated. It was revealed that an increase in laser power during LSM process could increase the surface roughness. The result shows that, the surface roughness of titanium alloy increased 27 times when modified with the highest laser power (27W) compared to the gritted surface. Furthermore, the modified surface by LSM will be heated using laser radiation in order to analyse the effect of surface roughness towards laser heating temperature. Depending on the value of the power during laser heating, the maximum temperature measured could be increased 27% corresponding to a gritted flat reference surface.

Preparation and characterization of polyacrylate emulsion pressure-sensitive adhesives with various lengths of fluorinated side chains

A series of fluorinated polyacrylate emulsion pressure-sensitive adhesives (PSA) with various lengths fluorinated side chains were synthesized by using n-butyl acrylate (nBA), acrylic acid (AA), 2-hydroxyethyl acrylate (HEA) together with three kinds of fluorine monomers trifluoroethyl methacrylate (TFEMA), hexafluorobutyl methacrylate (HFBMA) and dodecafluoroheptyl methacrylate (DFHMA). The influences of fluorocarbon chains’ length on the particle size of the latex, as well as on thermostability (DSC, TG) and surface properties (XPS, CA, AFM) of the PSA films were investigated. The results showed that T g and thermal stability of the PSA were both increased with the introduction of F-monomers with various lengths of fluorinated side chains, and the shorter the side chain, the more the T g and thermal stability increased. The XPS results indicated that the surface atom percentage of F element of film increased with the escalation of the length of fluorocarbon lateral chain, which results in the water contact angle and surface roughness increment of the PSA films. Finally, effects of fluorocarbon chains’ length on the adhesive properties (i.e. loop tack, peel strength and shear strength) of the fluorinated latex PSA were also evaluated.

Hydrothermal surface treatment of 434-L stainless-steel for spectra solar absorber application

This work aims to improve the absorption properties of stainless-steel (SS) (434-L) using a hydrothermal treatment method. Therefore, four SS films were prepared at different treatment times, i.e., 1 h, 2 h, 3 h and 24 h. The XRD results revealed the transformation of the crystal structure of the as-received SS from Body-centered cubic (BCC) to Face-centered cubic (FCC) of FeFe2O4 after treatment at 200 °C. The SEM results showed micro-pores distributed across the surface of the films, whereas the AFM results revealed an increment in surface roughness of the films as the duration of the treatment extended. The absorptance (α) of the SS was enhanced from 0.350 to 0.931 after the treatment. This improvement was attributed to surface oxidation and micro-pores distributed across the surface of the films, as confirmed by EDS and SEM results. On the other hand, the high emissivity (0.41) recorded was attributed to the large surface roughness (137.8 nm) of the film. Based on the UV–vis results, the optical reflectance of the film in the short wavelength of the solar spectrum was reduced from ~80 to ~8% resulting in a significant improvement in the absorptance of the SS.

Empirical study on ultrasonic assisted turn-milling

Turn-milling process has been paid attention in order to be used in multi-task machining processes. Moreover, looking for new machining techniques aimed at reducing cutting force is of important. Reducing cutting force in machining processes has the benefits of extending tool life and improving surface quality. One of the new concepts for reducing the cutting force is applying ultrasonic vibration. In this paper, effects of ultrasonic vibration under different machining parameters in turn-milling process of Al-7075 alloy will be investigated. In this order, a special mechanism was designed to apply ultrasonic vibration during machining process. Ultrasonic vibration exertion on the tool reduced cutting force and surface roughness up to 75% and 35%, respectively. Also tool rotational speed increment induced cutting force and surface roughness increment. In addition, tool feed rate and workpiece rotational speed increment caused cutting force and surface roughness increment. Although, feed rate was more influential.

A co-casting route enables the formation of skinless, hydrophobic poly(vinylidene fluoride) membranes for DCMD

Unlike the dual-layer membranes in which dual-layers attached tightly after co-casting, the attainment of independent poly (vinylidene fluoride) (PVDF) membranes with uniformly rough surface structures necessitates the delamination of top-layer membranes from the underlying PVDF membranes. The coverage of top-layer membranes via co-casting is expected to reduce the solvent/nonsolvent exchange rate for the underlying PVDF membranes during a phase inversion process. In this context, a polyethersulfone (PES) membrane was co-cast onto a PVDF membrane followed by phase inversion in a water bath to fabricate PVDF membranes for membrane distillation (MD). The spontaneous delamination of PES from PVDF membranes occurs once the membrane solidifies. Due to the combined effect of the additional PES layer and the solvent retained at the PES/PVDF interface, delayed liquid-liquid (L-L) demixing and crystallization of the PVDF solution take place during the phase separation process, resulting in the formation of a porous surface with symmetric cross-section. Results show that the PVDF concentration significantly affects the membrane morphology. Increasing the PVDF content from 16 wt% to 20 wt% leads to a marked morphological change for membrane cross-section from cellular pores to PVDF particles, which indicates that the phase inversion mechanism varies from delayed L-L demixing to solid-liquid (S-L) demixing; this is mainly affected by the solution viscosity. Due to the roughness increment by the particulate surfaces, the hydrophobicity of co-cast PVDF membranes (PVDF-co) is distinctly enhanced compared to the single-layer PVDF membranes. Furthermore, the pore sizes of the PVDF-co membranes are enlarged, and the thicknesses are reduced. Therefore, the PVDF-co membranes have much higher fluxes than the single-layer PVDF membranes, especially for PVDF-co-20 membranes composed of large PVDF particles which show superior pore interconnectivity than the cellular pores. A long-term stability test is conducted with the PVDF-20-21 membrane for 48 h using a 3.5 wt% NaCl solution at the feed and permeate temperatures of 60 °C and 20 °C, respectively. Fairly steady fluxes are observed over the testing course, as well as a continuous high salt rejection of above 99.95%

Microstructure and Fatigue Behavior of 2205/316L Stainless Steel Dissimilar Welded Joints

The relation among microstructure and fatigue behavior of 2205/316L stainless steel dissimilar welded joints was investigated. Plates of 6.35 mm in thickness with a single-V joint configuration were gas metal arc welded (GMAW) in a single pass by feeding at 6 m/min an ER2209 filler wire with a heat input of 1.2 kJ/mm. Grain growth in the high temperature-heat affected zone (HT-HAZ) occurred mostly at the mid-height of the plates, delimiting the width of this region up to ~1.28 and ~0.73 mm of the 2205 and 316L plates, respectively. Dilution of the 316L plate with the ER2209 filler altered the solidification mode in this side of the weld and led to a significant content of austenite along the fusion line. Fatigue tests were performed using sinusoidal waveform at room temperature applying uniaxial cyclic loading, between constant stress limits within the elastic deformation of tension and compression (Δσ) with stress ratio R = −0.3. With stress ranges of 98% and 95% the fatigue specimens rapidly failed in much less than 106 cycles. The failure crack initiated at the surface of the 316L in the HT-HAZ near the weld toe. Surface analyses of unbroken specimens before and after fatigue testing revealed a significant increment in roughness of the 316L base material owing to the formation of intrusions and extrusions.

High-Performance Natural Graphite-TiO2 Anode for Lithium-Ion Batteries: Using TiO2 Emulsion as a Solvent of Binder

In this study, an attempt has been made to improve the performance of natural graphite anode using TiO 2 nanoparticles. For this purpose, TiO 2 emulsion is used as a solvent of binder in the preparation of graphite anode slurry. In this method, high-performance electrodes have been achieved by combining two graphite and TiO2 nanoparticles constituents into an integrated structure. TiO 2 emulsions with different concentrations of 10%, 20%, and 100% are applied to prepare the binder solvent. The graphite anode made with 10% concentration of TiO 2 emulsion (NG-T10) shows the best performance in comparison with other samples. The Nano-scale images of the scanning electron microscope (SEM) affirm the existence of a uniform coating on the surface of the natural graphite particles for the NG-T10 electrode. Energy-dispersive X-ray (EDX) spectroscopy on the NG-T10 sample clearly indicates the Ti element signal. According to atomic force microscopy (AFM) images, an increment in surface roughness can provide a more effective surface and improve wettability, resulting in better electrochemical performance of NG-T10. The charge-discharge test of the NG-T10 half-cell represents an excellent cycle performance without any capacity degradation during 100 cycles at 0.5 C. However, the value of capacity retention for bare natural graphite (BNG) is 90.7% in the same conditions. The electrochemical impedance spectroscopy (EIS) results indicate that the existence of TiO 2 nanoparticles in NG-T10 improves the resistance of SEI film and charge-transfer resistance. The NG-T10 also enhances the pouch cell capacity at various current densities up to 4 C.

Mean and unsteady loading on square prisms with rounded edges: Hard marine growth, incidence, and Reynolds number effects

A set of wind tunnel experiments was performed to study the average and fluctuating wind loading on an ”infinite” 2D square prism with rounded edges of r/D = 0.16 for different heights of simulated hard marine growth at sub-to transcritical Reynolds numbers. It has already been shown, that a change in surface roughness from ks/D = 4.5×10−6 (smooth) to 1×10−3 (rough) on a similar prism at α = 0° and 45° had large effects on the widths and the Reynolds numbers marking the boundaries of the various flow states. At α = 45° it furthermore led to a large Reynolds-number independency of the lift and drag forces and of the Strouhal number. For the present wind tunnel tests two additional values of ks/D were selected to obtain smaller increments in surface roughness: 4.5×10-4 (slightly rough) and 1.4×10−3 (very rough). Mean and fluctuating lift and drag forces, the main vortex shedding frequency, distributions of the mean surface pressures in the mid-span cross-section of the prism and the mean wake profiles were recorded simultaneously. The same two static angles of incidence, α = 0° and 45°, were investigated for ReD = 60,000–12 million. For the prisms with smooth up to rough surfaces strong effects on the behaviour of all aerodynamic parameters with Reynolds number were found, whereas a further increase in ks/D induced hardly any additional effects. The absolute values of the aerodynamic parameters were found to be independent of a change in ks/D for the sub-to supercritical flow states. For the smooth and slightly rough prisms at α = 0° the supercritical flow state was present up to ReD = 12 million, whereas for the rougher prisms the upper transition and the transcritical flow states appeared at high Reynolds numbers. A change to α = 45° induced little variation with ks/D for all aerodynamic coefficients. The overall behaviour of the force coefficients and the Strouhal number with ks/D and ReD were caused by motions of the transition, separation and reattachment locations.

Wettability alteration of calcite rock from gas- repellent to gas-wet using a fluorinated nanofluid: A surface analysis study

Wettability alteration analysis form gas-repellent to gas-wet with the aid of chemical agents has been subjected of numerous studies. However, fundamental understanding of the effect of surface tension of liquid on repellency strength, the change in the intermolecular forces due to the adsorption of nanoparticles onto the rock surfaces, and exposure of treated rock in brine are not well discussed in the available literature. In this study, X-ray diffraction, Atomic Force Microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were applied to characterize the treated and fresh samples. Dynamic and static contact angle measurements were then combined with six methods of surface free energy analysis; Neumann, Zisman plot, geometric, harmonic, acid-base, and Chibowski, to model liquid intermolecular forces effect on contact angle and to calculate the surface forces. Surface characterization results showed that adsorbed fluorine and silicon elements onto the calcite surface due to treatment in the nanofluid resulted in an increment of surface roughness. The weight percent of 0.93 and 1.22 and surface fraction of 0.265 and 0.014 for adsorbed Fluorine and Silicon were observed, respectively. A reduction for surface free energy in the range of 20–35 mN/m was observed for different applied approaches. The results of geometric, harmonic, and acid-base models indicated that calcite intrinsically has a mildly polar surface with a negative surface charge. It was revealed that the magnitude of the dispersive component was nearly 1.6 times greater than the polar component. For the treated surfaces, the geometric, harmonic, and acid-base methods showed a high reduction in the polar force of surface (<4 mN/m), which implied that the dispersive forces of the surfaces were dominant (~13 mN/m). The acid-base model estimated a negative surface charge for calcite and treated calcite. Also, a reversible reduction in water repellency due to exposure of treated samples in brine was observed.

Effect of Ultrasonic Shot Peening on Oxidation Behavior of T91 and SS347 Steels in Air and Steam at 650 °C

Ultrasonic shot peening (USP) is a relatively new process of surface modification to improve mechanical properties as well as corrosion and high-temperature oxidation resistance of metallic materials. The effect of USP on surface properties and the process of high-temperature oxidation in air and steam environment, following USP of the T91 and SS347 steels, was studied in this investigation. Surface modification by USP was done on the T91 and SS347 steels for different time periods of 0.5, 1.0, 1.5, 2.0 and 3.0 min. Microstructural modification, increase in surface roughness and enhancement in microhardness up to a depth of 300-350 µm were observed due to USP. There was also increment in surface roughness as well as microhardness with USP time duration. Thermogravimetric analysis of the oxidation tests showed parabolic oxidation kinetics at 650 °C for both the steels. Comparatively more protective oxide scales, containing high amount of Cr, were formed on the USP-treated samples. The thickness of the oxide scale was reduced with increase in the USP time duration. Oxidation resistance of the T91 steel at 650 °C, both in air and steam, was improved by the USP treatment. Oxidation resistance of the SS347 steel at 650 °C was also improved for the USP2.0 and the USP3.0 conditions.

Shear Behavior of Artificial and Natural Granite Fractures After Heating and Water-Cooling Treatment

A clear understanding of shear behaviors of granite fractures with high temperatures undergoing water-cooling treatment is important in enhanced geothermal system (EGS). Two types of fractured Gonghe granite specimens, containing either a Brazilian-induced artificial fracture and or a pre-existing natural fracture, respectively, were considered. Before direct shear tests, all specimens were suffered from slow heating and rapid water-cooling treatment, and the thermal treatment temperatures ranged from room temperature 25 °C (without thermal treatment) to 300 °C. Shear properties of natural fractures, including shear strength, shear stiffness and shear dilation, are lower than that of the artificial fractures, mainly ascribed to their lower surface roughness than the artificial ones. Better matching in the artificial fractures after thermal treatment contributes to the increase in peak shear strength. The roughness increment or reduction after thermal treatment is insignificant. The thermal treatment results in the larger sheared-off asperities damage volume after shear in the artificial and natural fractures than that without thermal treatment. There is a strong correlation between the shear stress and acoustic emission (AE) parameters in both artificial and natural fractures. The AE responses in natural fractures are weak compared to that in artificial fractures. AE events distribute uniformly near the fracture surface in artificial specimens but present dispersedly in the natural ones.

Development of indium doped ZnO thin films for highly sensitive acetylene (C2H2) gas sensing

Abstract The proposed article presents optimized Indium doped ZnO thin film for acetylene gas sensor. Thin films of ZnO and Indium doped ZnO of thickness 100 nm were successfully deposited on glass substrate using resistive thermal evaporation method. Structural properties have been performed by using XRD which reveals polycrystalline nature of the thin films. Morphological studies have been performed by using FESEM which reveals the information that thin film is homogeneous and uniform. AFM showed that with the increasing of indium doping concentration in ZnO resulting increment in vertical roughness of thin films. Further sample were tested for acetylene gas sensing using Keithley source meter and multimeter. The fabricated sensor (IZO-3) showed high sensitivity magnitude of 29.06 (100 ppm), short response and recovery time of 49.28 s and 58.45 s respectively at 150 °C operating temperature. IZO-3 sensor showed good linearity with good selectivity and excellent reproducibility.

Hollow cathode plasma nitriding of medical grade Ti6Al4V: A comprehensive study.

Ti6Al4V used in biomedical applications still has several surface-related problems, such as poor bone compatibility and low wear resistance. In this work, the formation of a protective layer of titanium nitride obtained by plasma treatment in hollow cathode was studied, and the best experimental conditions were verified by a statistical factorial design of experiments. The samples were characterized in terms of their physical and chemical properties, correlating the effects of time (min) and temperature (°C). An achieved ideal condition was further analysed in terms of in vitro cytotoxicity, micro-abrasion, and electrochemical properties. The carried-out assessment has shown that nitrided condition has an improvement in wettability, microhardness, along with TixNy formation and roughness increment, when compared to pristine condition.

An experimental and numerical study of micro-grinding force and performance of sapphire using novel structured micro abrasive tool

Micro-grinding technology has more competitive advantages than other micro machining technologies in fabricating complex three-dimensional micro parts and micro structures on hard and brittle materials, but the service life of existing micro abrasive tool has become one of the key factors restricting the popularization and application of micro-grinding technology. In this study, a novel structured micro abrasive tool with chip removal micro helical slots and the diameter less than 700μm is designed and prepared by hybrid process aimed at reducing wear and tear and increasing the service life of micro abrasive tool. The micro-grinding force model considering the structural parameters, size effect and material removal mechanism is established, which can reflect the micro-grinding performance and wear resistance of the novel micro abrasive tool. The verified experimental results indicated that the micro-grinding force model can effectively predict time-domain variation of the novel structured micro abrasive tool, and the simulated grinding force signal within 150ms fluctuation range error can be confined to be 7%. Moreover, comparing with the conventional micro abrasive tool, the micro-grinding force of sapphire specimens machined by novel micro abrasive tool is significantly reduced. Besides, the novel micro abrasive tool shows better wear resistance with the increase of grinding times, the novel micro abrasive tool surface roughness increment ∆Ra1 and ∆Rz1 is decreased by 0.2μm and 10μm respectively, and the stability of micro grinding is markedly improved. This work might play an important role in promoting the parameterization and non-standardization design of micro abrasives tools.

Development of Silicon Carbide Atomic Layer Etching Technology

Silicon carbide (SiC) is an emerging material for applications in ultra-precision devices and space optics due to its low thermal expansion characteristics (3.8×10−6/℃) and light density (3g/cm³). However, machining and polishing of SiC are challenging because of its hardness and stiffness. Further, the conventional mechanical processing methods could result in micro-cracks on the surface of SiC, which consequently degrade the lifetime of the device under harsh conditions. We find that very smooth polishing of SiC without any surface damage is possible using plasma atomic layer etching, an emerging technology in the field of semiconductor manufacturing. In the present study, we conducted experiments to identify the mechanism of plasma atomic layer etching for bi-atomic materials and elucidated the optimized processing conditions to minimize the surface roughness of the etched SiC. By using process gases, such as SF6, H2, and O2, the etch rate could be controlled and the increase in the surface roughness could be minimized. We identified three main reasons for the increase in the surface roughness. The first is different etching speed of the silicon and carbon by fluorine active species. The second is the masking effect of C-H-F films produced during process. The last is the selective etching of silicon oxide and the other layers by fluorine active species. Due to the low etching property of silicon oxides, the surface roughness may increase at a faster rate under rich oxygen condition. Conversely, it is possible to minimize the surface roughness by adjusting the ratio of process gases. Under the optimum conditions of SF6 and O2 gas ratio (0.8), the etch rate of 1 layer/cycle and the roughness increment of 0.1 nm were obtained

The effect of particle size and phosphorous content in biomineralization media on in vitro bioactivity of monticellite based ceramic powders obtained from boron derivative waste

The effect of particle size and phosphorous content in biomineralization media on in vitro bioactivity of monticellite based ceramic powders was investigated. Monticellite based ceramic powder was synthesized at 800°C for 4h using boron derivative waste. Monticellite based ceramic powder, comprising monticellite, akermanite, diopside, calcium magnesium borate and zeolite LTA crystalline phases, was crushed and then ball-milled for optimized time to obtain lowest average particle size and the narrowest particle size distribution. In vitro bioactivity of both coarse (d10: 0.5μm, d50: 3.0μm, d90: 42μm) and fine (d10: 0.5μm, d50: 1.4μm, d90: 4.8μm) wafers was determined by incubation in Lactated Ringer's Solution and Human Blood Plasma for 1, 3, 5, 7, 14, 21 and 28 days at 36.5±0.5°C. The obtained results exhibited that calcite (CaCO3) layer after immersion in Lactated Ringer's Solution and bone-like apatite layer after immersion in Human Blood Plasma were formed on the surface of coarse and fine wafers. The presence of phosphorus in biomineralization media is necessary for apatite formation. The increment of surface roughness favors homogeneous nucleation, and fasten nucleation and growth kinetics of precipitation. As a result, the bioactive characteristic of monticellite based ceramic powder could be governed by the particle size.

Impact of rock fragment size on erosion process and micro-topography evolution of cone-shaped spoil heaps

Spoil heaps in sites disturbed by construction cause severe acceleration of erosion, threatening environment quality and personal safety. Rock fragments (RFs) are a common component of spoil heaps; therefore, this study was conducted to evaluate the effects of different size classes of RFs on cone-shaped spoil heap erosion. A 3D laser scanner was used to capture the surface micro-topography evolution. A multi-day rainfall simulation experiment at 1.5 mm min−1 rainfall intensity was conducted with 30 mass percent of RFs of different diameters (1–3.5, 3.5–7, 7–10, 10–15 cm). The results showed that RFs reduced runoff by 13.0% relative to the bare soil spoil heap, among which the RFs of the 7–10 cm size class performed best. Only the initial surface micro-topography factors increased with RF size. The stable micro-topography factors of 1–3.5 cm RF treatment were 59.2% larger than those for other RF treatments on average because of the slope slump. Spoil heaps containing small size (1–3.5) RFs more easily slumped with an area of 0.895 m2 and showed obvious changes in micro-topography. RFs in different size classes influenced soil loss of spoil heaps via runoff yield and effects on slope stability. Larger roughness increment and runoff rate were associated with greater soil loss rate (R2 = 0.828), but time-varying roughness had no effect on runoff. Overall, the results of this study provide a better understanding of the impact of RFs on spoil heap erosion.