Increase In Surface Roughness Research Articles

The effects of medium and friction pair on the tribological behavior of Mo-doped DLC films

Diamond-like carbon (DLC) films are widely used to improve the tribological properties of key components in internal combustion engines. However, their performance can be significantly affected by the service environment, which may impact engine reliability. This study investigates the impact of various media and friction pairs on the tribological behavior of molybdenum-doped DLC (Mo-DLC) films. The results demonstrate that Mo-DLC films exhibit excellent tribological properties across different media, showcasing their adaptability to various conditions. The lubrication mechanism varies with media viscosity: in methanol, Mo-DLC films operate under boundary lubrication conditions, leading to a relatively high wear rate of approximately 5.2 × 10−8 mm3/N·m. Conversely, in diesel and polyalphaolefin-based oil (PAO), where fluid dynamic lubrication occurs, wear rates are significantly lower, at 4.4 × 10−8 mm3/N·m and 3.1 × 10−8 mm3/N·m, respectively. In addition, the friction pair significantly influences the tribological performance of the Mo-DLC film. When paired with D-GCr15 in methanol, Mo-DLC films exhibit a low friction coefficient of 0.09 and a wear rate of 1.6 × 10−8 mm3/N·m, respectively. However, when coupled with N-GCr15, the increased surface roughness extends the running-in period and raises the friction coefficient in methanol. These findings offer valuable theoretical insights and practical guidance for optimizing DLC films in internal combustion engines.

Effect of Nanoscale Surface Roughness and Electron-Phonon Interaction on Vibrational Modes of Cadmium Telluride Using Resonant Raman Spectroscopy.

This study investigates the combined effects of nanoscale surface roughness and electron-phonon interaction on the vibrational modes of cadmium telluride (CdTe) using resonant Raman spectroscopy. Raman spectra simulations aided in identifying the active phonon modes and their dependence on roughness. Our results reveal that increasing surface roughness leads to an asymmetric line shape in the first-order longitudinal optical (1LO) phonon mode, attributed to an increase in the electron-phonon interaction. This asymmetry broadens the entire Raman spectrum. Conversely, the overtone (second-order longitudinal optical [2LO]) mode exhibits a symmetrical line shape that intensifies with roughness. Additionally, we identify and discuss the contributions of surface optical phonon mode and multiphonon modes to the Raman spectra, highlighting their dependence on roughness. This work offers a deeper understanding of how surface roughness and electron-phonon scattering influence the line shape of CdTe resonant Raman spectra, providing valuable insights into its vibrational properties.

The effect of simulated food liquids on the surface structure and solubility of various esthetic restorations

Aims: The aim of this study is to investigate the surface roughness and solubility of restorative materials when exposed to foodstuffs in the oral environment using simulated food liquids as defined by the Food and Drug Administration. Methods: In this study, a total of four esthetic restorative materials were used: one universal compomer (Dyract XP, Dentsply), one conventional microhybrid composite (FiltekTM Z250, 3M ESPE), one nanofilled, and one high-viscosity glass ionomer cement (ChemFil Rock, Dentsply). A total of 160 samples, each 8 mm in diameter and 2 mm in thickness, were prepared using molds. The initial weights of the samples were recorded in micrograms using a precision balance to determine solubility values. Initial surface roughness values were measured using an atomic force microscope device. The samples were immersed in four different simulated food liquids (ethanol, heptane, citric acid, and distilled water) for a period of 7 days. After removal from the solutions, the samples were desiccated to a constant weight, and the second set of weights was recorded. Subsequently, the second surface roughness values were measured Results: Among the materials immersed in the simulated food solutions, ChemFil Rock exhibited the highest solubility and increase in surface roughness. Citric acid was found to be the solution that caused the highest increase in surface roughness values and solubility for this material (p

Assessment of the effect of experimental gel of pregabalin associated with 35% hydrogen peroxide bleaching on bovine dental enamel: an in vitro study.

To assess the effect of bleaching with gel of pregabalin associated with 35% hydrogen peroxide on the mechanical and chemical properties and ultramorphology of dental enamel. Thirty-six (36) specimens of bovine dental incisors were obtained and divided into three groups (n = 12), namely: CG = bleaching with 35% hydrogen peroxide; KFG = bleaching with 5% potassium nitrate and 2% sodium fluoride gel + 35% hydrogen peroxide; and PGG = bleaching with experimental gel of pregabalin + 35% hydrogen peroxide. The specimens were assessed with respect to Knoop microhardness, surface roughness, and colour change, before and after bleaching. They were also assessed using scanning electron microscopy and energy-dispersive spectroscopy after treatments. All groups exhibited an increase in surface roughness and a reduction in Knoop microhardness after the protocols. There was colour change in all groups, with no difference between them. In addition, there were changes in enamel morphology and non-significant loss of calcium and phosphorus. The experimental gel of pregabalin did not influence the action of 35% hydrogen peroxide, yielding results similar to those of the other groups assessed in all the parameters. Therefore, the gel of pregabalin can be an alternative for topical application on the surfaces of the teeth in association with bleaching treatments.

Nanoscale Perturbations of Lipid Bilayers Induced by Magainin 2: Insights from AFM Imaging and Force Spectroscopy

This study explores the impact of the antimicrobial peptide magainin 2 (Mag2) on lipid bilayers with varying compositions. We employed high-resolution atomic force microscopy (AFM) to reveal a dynamic spectrum of structural changes induced by Mag2. Our AFM imaging unveiled distinct structural alterations in zwitterionic POPC bilayers upon Mag2 exposure, notably the formation of nanoscale depressions within the bilayer surface, which we term as "surface pores" to differentiate them from transmembrane pores. These surface pores are characterized by a limited depth that does not appear to fully traverse the bilayer and reach the opposing leaflet. Additionally, our AFM-based force spectroscopy investigation on POPC bilayers revealed a reduction in bilayer puncture force (FP) and Young's modulus (E) upon Mag2 interaction, indicating a weakening of bilayer stability and increased flexibility, which may facilitate peptide insertion. The inclusion of anionic POPG into POPC bilayers elucidated its modulatory effects on Mag2 activity, highlighting the role of lipid composition in peptide-bilayer interactions. In contrast to surface pores, Mag2 treatment of E. coli total lipid extract bilayers resulted in increased surface roughness, which we describe as a fluctuation-like morphology. We speculate that the weaker cohesive interactions between heterogeneous lipids in E. coli bilayers may render them more susceptible to Mag2-induced perturbations. This could lead to widespread disruptions manifested as surface fluctuations throughout the bilayer, rather than the formation of well-defined pores. Together, our findings of nanoscale bilayer perturbations provide useful insights into the molecular mechanisms governing Mag2-membrane interactions.

Influence of surface roughness on vibration response characteristics of flexible structures on offshore floating platforms

The expanding interest in floating offshore renewable energy technologies, including floating wind turbines and solar platforms, is attributed to their multifarious benefits. One pivotal factor influencing the power generation efficiency of these technologies is the vibration response of the flexible structures connected to the platforms, such as mooring systems, dynamic power cables, and flexible pipelines. In this research, a numerical investigation is conducted on the response characteristics of vortex-induced vibration (VIV) of cylinders with varying surface roughness in oscillatory flow. The unsteady Reynolds-averaged Navier-Stokes (URANS) equations and dynamic equation are used for fluid-structure interaction. The results reveal that for rough cylinders, multiple frequencies are involved in the vibration. For most simulated cases, the vibration frequency in the cross-flow (CF) direction is an integer multiple of the frequency of the oscillatory flow and associated with the quantity of shedding vortex pairs during a single period of the oscillatory flow. For rough cylinders, the CF vibration frequency differs by one from the number of shedding vortex pairs within one period of the oscillatory flow. With the increase of surface roughness, the maximum vibration amplitude shows an increasing trend (12%), then a decreasing trend (21%). Furthermore, the vortex shedding flow pattern presents C + S mode or S mode. This study offers valuable insights for analyzing the vibration response characteristics of authentic flexible structures.

Surface modification of polyester fabrics using choline hydroxide-catalysed glycolysis

This study explores the surface modification of polyethene terephthalate (PET) fabric via glycolysis, employing choline hydroxide as an eco-friendly catalyst. A range of chemicals was evaluated for catalysing the glycolysis reaction. Among them, choline hydroxide demonstrated notable enhancements in surface hydrophilicity, moisture regain, wicking properties, and water contact angle, surpassing other catalysts. Scanning Electron Microscopy (SEM) revealed a marked increase in surface roughness and irregularities following glycolysis in the presence of this ionic liquid. The surface modification technique employed in this investigation resulted in a decrease of less than 20% in the breaking force of the fabric. Fourier Transform Infrared (FT-IR) spectroscopy and the methylene blue staining method confirmed the emergence of free hydroxyl groups on the modified fabric's surface. These findings suggest that glycolysis catalysed by choline hydroxide is a promising approach for enhancing the surface characteristics of polyester fabrics, which may lead to improved functional properties in textile applications.

The Effective Capacitance Behaviour of Argon Plasma Exposed Al Dopped CdO Electrode Used in Efficient Metal ‐Air Batteries

AbstractThe impact of employing DC glow discharge plasma on aluminum‐doped cadmium oxide (Al‐doped CdO) electrodes is explored in the context of advanced energy storage, particularly focusing on Al‐air batteries. Utilizing various characterization techniques including XRD, FTIR, Raman spectroscopy, FESEM, and EDS, we identify significant changes in structure and morphology induced by plasma treatment, such as nano scale clustering, increased surface roughness, and higher oxidation levels. Electrochemical tests with a three‐electrode system shows remarkable improvements in charge storage capacity after plasma treatment, particularly with argon plasma, resulting in increased capacitance (1140 Fg−1), specific capacity (681 mAhg−1), and reduced charge transfer resistance (4.2 Ω), with notable changes in behavior, especially in potassium hydroxide (KOH) electrolyte.

Marine Fouling Release Performance of Amphiphilic Carboxybetaine Perfluoropolyether Methacrylate Polymer Coatings

AbstractAmphiphilic polymer systems have been demonstrated to be an effective and environmentally friendly approach to combat the challenges of biofouling, especially in the real ocean environment. A variety of polymer compositions containing fluorophilic perfluoropolyether (PFPE) urethane dimethacrylate and zwitterionic carboxybetaine methacrylate (CBMA) are in situ copolymerized across a broad concentration range and anchored to chemically functionalized substrates by grafting‐through polymerization. Dynamic accumulation assays with the marine diatom Navicula perminuta and the marine bacterium Cobetia marina revealed an enhanced antifouling performance in most of the amphiphilic polymer mixtures when zwitterionic units are combined with hydrophobic PFPE compounds. It is noticed that the resulting polymer networks still possess enough orientational freedom to quickly rearrange in the presence of water. It is further observed that several of the very hydrophilic formulations and some of the moderately hydrophobic formulations exhibit low fouling against the marine fouling organisms Navicula perminuta and Cobetia marina. This correlated with increased surface roughness and the ability for underwater rearrangement. Furthermore, it is discussed whether the probability that highly hydrated hydrogels, which appear sponge‐like, may create a diffuse interphase which promotes the incorporation of silt. Latter is counteracted by the hydrophobic PFPE building blocks in the amphiphilic coatings.

Microstructural and micromechanical evolution features of asphalt with aging: An atomic force microscopy study

This study explores the aging effects on matrix asphalt (MA) and styrene-butadiene-styrene modified asphalt (SBSMA) using atomic force microscopy (AFM). Aging was simulated with the rolling thin-film oven test (RTFOT) and the pressure aging vessel (PAV) test. Key changes in microtopography, surface roughness, adhesive forces, Young's modulus, and energy dissipation were analyzed. The findings reveal significant microstructural changes with aging, including an increase in the size and a decrease in the number of beelike structures, increased surface roughness, and Young's modulus, which indicate material hardening. The analysis shows a reduction in adhesive force and energy dissipation, suggesting increased brittleness and viscosity. Notably, SBSMA exhibits better aging resistance than MA, as demonstrated by its lower roughness, stronger adhesive forces, and less reduction in energy dissipation, highlighting the effectiveness of the SBS modifier in mitigating aging impacts. These results underscore the critical role of material composition in the aging behavior of asphalt binders.

In-Vitro Comparison of Titanium Disc Surface Roughness and Bacterial Colonization after Ultrasonic Instrumentation with Three Different Tips.

During implant maintenance, preserving a smooth surface on the machined trans-mucosa abutment is critical to reduce biofilm attachment and colonization. The present study compare the surface roughness and bacterial colonization of machined titanium surfaces after instrumentation with various materials. Forty-four machined Grade 23 titanium discs were instrumented with a round Polyether Ether Ketone (PEEK) tip, a plastic curette tip, or a pure titanium curette tip with piezoelectric devices. Before and after instrumentation, the surface roughness (Ra and Rz) values were analyzed with a profilometer and scanning electron microscopy (SEM). Streptococcus sanguinis was cultured and incubated for 24 hours on the instrumented discs, and colony-forming units (CFU)/mL were obtained for each group. Samples instrumented with the metal ultrasonic tip significantly increased surface roughness compared to the other groups. Thisresulted in greater colonization by S. sanguinis than surfaces instrumented with PEEK tips or the negative control. Samples instrumented with PEEK and plastic tips did not exhibit any statistically significant increase in surface roughness. SEM analysis revealed a significantly rougher surface of discs instrumented with metal compared to discs instrumented with plastic or PEEK tip, despite the possibility of debris from tip dissolution. Our results suggested that instrumentation with metal ultrasonic tips with piezoelectric devices significantly increase machined titanium's surface roughness and elicited higher biofilm formation in vitro. Meanwhile, instrumentation of machined titanium with PEEK or plastic ultrasonic tips did not affect the surface roughness or bacterial adhesion.

From surface to success: How implant surfaces shape osseointegration

The field of dental implantology has significantly advanced to address the multifaceted impacts of tooth loss, encompassing physical, functional, emotional, psychological, and social dimensions. Dental implants serve as reliable solutions, ensuring stability, minimal bone loss, and absence of pain or infection. Central to their success is the surface modification of implants, which profoundly influences osseointegration—the process crucial for establishing a functional bond between bone and implant. This review explores various physical modifications of dental implant surfaces, focusing on macro, micro, and nano-level alterations. Macro-level modifications optimize implant geometry and thread design to enhance initial stability and long-term fixation. Micro-level modifications, including grit blasting and acid etching, increase surface roughness to facilitate mechanical interlocking and cell adhesion. Nano-level modifications, such as hydrophilic coatings and bioceramic enhancements, enhance surface energy and promote osteoblastic differentiation, thereby accelerating osseointegration. These surface modifications represent a critical frontier in implant dentistry, promising improved clinical outcomes and patient satisfaction through enhanced integration and reduced healing times.

Enterobacter cloacae-mediated polymer biodegradation: in-silico analysis predicts broad spectrum degradation potential by Alkane monooxygenase.

Plastic pollution poses a significant environmental challenge. In this study, the strain Enterobacter cloacae O5-E, a bacterium displaying polyethylene-degrading capabilities was isolated. Over a span of 30days, analytical techniques including x-ray diffractometry, scanning electron microscopy, optical profilometry, hardness testing and mass spectrometric analysis were employed to examine alterations in the polymer. Results revealed an 11.48% reduction in crystallinity, a 50% decrease in hardness, and a substantial 25-fold increase in surface roughness resulting from the pits and cracks introduced in the polymer by the isolate. Additionally, the presence of degradational by-products revealed via gas chromatography ascertains the steady progression of degradation. Further, recognizing the pivotal role of alkane monooxygenase in plastic degradation, the study expanded to detect this enzyme in the isolate molecularly. Molecular docking studies were conducted to assess the enzyme's affinity with various polymers, demonstrating notable binding capability with most polymers, especially with polyurethane (-5.47kcal/mol). These findings highlight the biodegradation potential of Enterobacter cloacae O5-E and the crucial involvement of alkane monooxygenase in the initial steps of the degradation process, offering a promising avenue to address the global plastic pollution crisis.

Enhance PD/A biofilm formation via a novel biochar/tourmaline modified-biocarriers to treat low-strength contaminated surface water: Initial adhesion and high-substrate microenvironment

In this work, a novel polyurethane carrier modified with biochar and tourmaline/zeolite powder at ratio of 1:1 and 1:2 was developed to promote the formation of biofilms and the synergy of overall bacterial activity for Partial Denitrification/Anammox to treat low-nitrogen contaminated surface water. Based on the batch experiment, the modified biocarrier, BTP2 (biochar: tourmaline = 2: 1), exhibited the highest total nitrogen removal efficiency (83.63%) under influent total nitrogen of 15 mg/L and COD/NO3− of 3. The dense biofilm was formed in inner side of biocarrier owing to the increased surface roughness and various functional groups suggested by scanning electron microscopy and Fourier-transform infrared analysis. The EPS content increased from 200.15 to 220.26 mg/g VSS in BTP2 system. Besides, the rapid NH4+ capture and organics release of the modified carrier fueled the growth of anammox and denitrification bacteria, with the activity of 2.13 ± 0.52 mg N/gVSS/h and 6.70 ± 0.52 mg N/gVSS/h (BTP2). High-throughput sequencing unraveled the increased abundances of Candidatus_Competibacter (0.82%), Thauera (0.60%) and Candidatus_Brocadia (0.55%) which was responsible for the synergy of incomplete reduction of NO3− to NO2− and NH4+ oxidation. Overall, this study provided a valid and simple-control guide for biofilm formation towards rapid enrichment and great collaboration of Anammox and denitrification bacteria.

Wettability-Oriented Laser Microgrooving Process on Cemented Carbide Surface.

Surface micro-texture has been shown to enhance wettability and reduce wear on cutting tools. However, there is limited research on how laser parameters impact the dimensional accuracy of surface texture and its wettability. This study focuses on producing arrayed groove textures on WC/Co cemented carbide surfaces using Nd: YAG laser, evaluating the effect of the laser parameters on surface topography and texture accuracy through microscopic observation and simulation. The results indicate that, with laser parameters such as a number of passes less than 5, approximately 16 W power, scanning speed of 100-150 mm/s, and pulse frequency of 30 kHz, the error between the groove width and laser spot diameter was 4.7%. Additionally, the study explores the impact of the groove texture on surface wettability using the solid droplet method and XPS analysis. Comparative experiments reveal that increased surface roughness enhanced oleophobicity, with surfaces exhibiting high texture accuracy and integrity showing improved oleophobic and spreading properties. Thus, the precise regulation of laser processes is crucial for maintaining surface texture integrity and enhancing surface wettability.

Effect of surface pretreatment on the polypyrrole coating of acrylonitrile butadiene styrene. Part A: Synthesis and characterization

This paper investigates the synergistic effects of a two-step surface modification approach on acrylonitrile butadiene styrene (ABS) plastics. The first step involves a mechanical grinding pretreatment followed by chemical etching in sulfuric acid and hydrogen peroxide, which increases surface roughness and enhances the wettability of the ABS surface. The second step focuses on the chemical synthesis of polypyrrole (PPy) on the pretreated ABS, demonstrating improvements in PPy surface roughness and adhesion after grinding and chemical etching. Adhesion tests reveal a significant increase from 0 % (PPy on untreated ABS) to 66 % (PPy on the grounded ABS) and ultimately to 100 % (PPy on the grounded ABS after chemical etching). This research is dedicated to a comprehensive exploration of the fundamental mechanisms, substantiated by a rigorous analysis involving X-ray photoelectron spectroscopy (XPS) examination, scanning electron microscopy (SEM) and contact angle measurements. Furthermore, the electric conductivity of PPy coatings is enhanced through electrochemical doping of PPy using dodecyl sulfate anions (DS/PPy/ABS) and the incorporation of silver particles (Ag/PPy/ABS). Raman spectroscopy demonstrates the Surface-Enhanced Raman Scattering (SERS) effect of silver particles on PPy coatings, showcasing their interaction. X-ray diffraction (XRD) confirms the enhanced crystallinity of DS/PPy/ABS, aligning with increased conductivity after electrochemical doping with DS anions.

Selective double-layer on black Ni-P enhances solar absorption and reduces corrosion

This work investigates a double-layer configuration for the black Ni-P layers used in solar adsorption technology, aiming to increase the absorption of a broader range of solar wavelengths. This multilayer configuration has a surface with increased roughness and absorption area. The valleys were porous materials, which were connected to an underlying metallic sub-layer that is susceptible to corrosion. In turn, this corrosion induced changes to the top layer. The Ni-P layer was deposited by the electroless technique using an acid nickel sulfate bath as a source of metal ions and a reducing agent of sodium hypophosphite. Etching initiated an oxidation process on the surface, forming a layer of amorphous black nickel oxide for absorption. The surface features of the black Ni-P double layer consist of an uneven surface that aids sunlight adsorption. Carbon steel (AISI 1018) with different surface finishes was used for depositing Ni-P and black Ni-P, aiming to establish correlations with solar adsorption. The sample with an increased surface roughness obtained a higher absorption percentage than a single layer. The corrosion rate was calculated as 7 mmpy for the black Ni-P layer by applying polarization curves. A 6 µm-thick Ni-P double layer was obtained, achieving 96% absorption within the 300–2,000 nm range.

Minimum cutting thickness prediction model for micro-milling machining and experimental Study of FeCoNiCrMn high-entropy alloy machining

FeCoNiCrMn high entropy alloy has excellent properties such as high hardness, high strength and high wear resistance, which has a broad application prospect in aerospace, military and other fields. As an emerging difficult-to-machine material, the minimum cutting thickness determines the highest machining accuracy of micro-milling. In order to improve the micro-milling quality of FeCoNiCrMn high-entropy alloy, a minimum cutting thickness prediction model based on the effective front angle of the tool is established according to the analysis of micro-milling force model. Through the FeCoNiCrMn high-entropy alloy micro-milling processing experiments, the milling force parameters are calculated by substituting them into the prediction model, and the minimum cutting thickness value of FeCoNiCrMn high-entropy alloy is 1.367 μm when the flank radius of the milling cutter is 5 μm.When the feed rate of each tooth is in the range of 1 μm–1.5 μm, the severe size effect and the ploughing effect lead to the specific cutting energy nonlinearly increase, and the cutting force and surface roughness increase sharply with large fluctuations. From this, the range of the minimum cutting thickness of the high-entropy alloy was judged to be between 1 μm and 1.5 μm, and the accuracy of this prediction model was verified.

The effects of plastisphere on the physicochemical properties of microplastics.

The plastisphere is the microbial communities that grow on the surface of plastic debris, often used interchangeably with plastic biofilm or biofouled plastics. It can affect the properties of the plastic debris in multiple ways. This review aims to present the effects of the plastisphere on the physicochemical properties of microplastics systematically. It highlights that the plastisphere modifies the buoyancy and movement of microplastics by increasing their density, causing them to sink and settle out. Smaller and film microplastics are likely to settle sooner because of larger surface areas and higher rates of biofouling. Biofouled microplastics may show an oscillating movement in waterbodies when settling due to diurnal and seasonal changes in the growth of the plastisphere until they come close to the bottom of the waterbodies and are entrapped by sediments. The plastisphere enhances the adsorption of microplastics for metals and organic pollutants and shifts the adsorption mechanism from intraparticle diffusion to film diffusion. The plastisphere also increases surface roughness, reduces the pore size, and alters the overall charge of microplastics. Charge alteration is primarily attributed to changes in the functional groups on microplastic surfaces. The plastisphere introduces carbonyl, amine, amide, hydroxyl, and phosphoryl groups to microplastics, causing an increase in their surface hydrophilicity, which could alter their adsorption behaviors for heavy metals. The plastisphere may act as a reactive barrier that enhances the leaching of polar additives. It may anchor bacteria that can break down plastic additives, resulting in decreased crystallinity of microplastics. This review contributes to a better understanding of how the plastisphere alters the fate, transport, and environmental impacts of microplastics. It points to the possibility of engineering the plastisphere to improve microplastic biodegradation.

Influence of discrete laser surface melting on hot cracking behavior and mechanical properties of Q235 steel

Modern industries demand higher mechanical properties from components. Traditional heat treatment methods often suffer from drawbacks such as high production costs, time-intensive processes, and labor-intensive procedures. The integration of bionic engineering with laser surface melting has given rise to Discrete Laser Surface Melting (DLSM) technology, effectively mitigating these shortcomings. Previous research has substantiated the capability of this technology to significantly enhance various metal properties. This study employed an Nd:YAG pulsed laser for the DLSM treatment of Q235 steel. The discrete laser surface melted (DLSMed) units were prepared on Q235 steel samples. Subsequent analysis utilized scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive spectroscopy (EDS) to examine the microstructure and chemical composition of the DLSMed samples. Surface profilometry, hardness testing, and X-ray stress testing were conducted to measure surface roughness, microhardness, and residual stress, respectively. Mechanical properties were evaluated using tensile and impact testing machines. Experimental findings revealed that the DLSMed sample's surface could be divided into three regions: the melting zone, the heat-affected zone (HAZ), and the substrate. The microstructure of the melting zone consisted of refined martensite. The depth and width of the DLSMed units exhibited a certain regularity with variations in the defocus distance. Increasing the defocus distance positively impacted grain refinement and hardness but also led to an increase in surface roughness. Residual stress increased within a specific defocusing range, but beyond this range, its variation lost regularity. Hot cracking behavior within the DLSMed unit encompassed four stages: crack nucleation, propagation, healing, and decomposition. Different defocusing distances and the distribution of DLSMed units significantly affected the tensile strength and impact toughness of the samples. As the defocusing distance increased, the tensile and yield strength of DLSMed samples with transverse units gradually decreased. In contrast, samples with longitudinal units showed a trend of first decreasing and then increasing in tensile and yield strength. The distribution of DLSMed units played a significant role in improving the tensile properties of Q235 steel. The contribution of three factors to the impact performance of DLSMed samples was ranked from high to low as hardness, grain size, and yield strength ratio. The soft phase (substrate) could absorb impact energy and convert it into strain energy stored in the DLSMed sample. Only when the distribution of DLSMed units (hard phases) aligned with the tensile direction could they effectively limit the plastic deformation and enhance the mechanical properties of Q235 steel. However, an increase in defocusing distance led to increased brittleness, deteriorating the mechanical properties of the DLSMed samples. Finally, this study unveiled the strengthening mechanisms of DLSMed samples, providing valuable insights for future applications in enhancing the mechanical properties of metals.