Formation Mechanism Of Morphology Research Articles

Experimental and numerical investigations on interface microstructure characteristics and wave formation mechanism of Sn/Cu explosive welded plates

ABSTRACT The interface characteristics and formation mechanism of explosive welded waveform structures still lack a detailed and in-depth research. Thus, a combination of advanced characterization and numerical simulation methods were performed in this study to investigate the phase constitution, texture distribution, 3D interface morphology and wave formation mechanism of Sn/Cu explosive welded interface. The microstructure analyses indicated that the typical waveform structures composed of fine crystal band and elongated grains zone were formed at the Sn/Cu joining interface. The dynamic recrystallized structures and local high strain at the waveform were attributed to severe rheological deformation and rapid solidification of liquid metals. In addition, the S, copper, brass and fiber deformation textures and the cube and gross recrystallization textures were found. The CT results indicated the 3D Sn/Cu joining interface morphology presents a regular convex waveform feature, which is related to periodic pulse load caused by explosive detonation. Furthermore, based on the simulation results, the 2D joining interface presents similar experimental waveform structure, and the 3D interface evolution characteristic was consistent with the shock wave propagation characteristics on the flying plate to some extent, which was in good agreement with the experimental results.

Chalcogenide glass nanospheres with tunable morphology by liquid-phase template approach

Chalcogenide glass (ChG) with unique material properties has been widely used in mid-infrared. Traditional ChG microspheres/nanospheres preparation usually uses a high-temperature melting method, in which it is difficult to accurately control the size and the morphology of the nanospheres. Here, we produce nanoscale-uniform (200-500nm), morphology-tunable, and arrangement-orderly ChG nanospheres from the inverse-opal photonic crystal (IOPC) template by the liquid-phase template (LPT) method. Moreover, we refer to the formation mechanism of nanosphere morphology as the evaporation-driven self-assembly of colloidal dispersion nanodroplets within the immobilized template and find that the concentration of ChG solution and the pore size of IOPC are the key to control the morphology of the nanospheres. The LPT method is also applied to the two-dimensional microstructure/nanostructure. This work provides an efficient and low-cost strategy for the preparation of multisize ChG nanospheres with tunable morphology and is expected to find various applications in mid-infrared, optoelectronic devices.

Comparison of melt evolution and flow mechanisms of Inconel 718, Ti6Al4V, 304 stainless steel, and AlSi10Mg manufactured by laser powder bed fusion, structures, and properties after heat treatments

Process parameters and material type are the key influencing factors in laser powder bed fusion (LPBF) manufacturing. In this study, a three-dimensional high-fidelity discrete heat-flow-coupled model was developed to study the surface morphology, melt evolution, and defect formation mechanisms of four types of alloys formed using LPBF under different laser processes at the powder scale to optimize the process parameters. Four alloys were manufactured by LPBF with optimal process parameters. Multiple characterizations were adopted to disclose the effect of heat-treatment on the microstructure and mechanical properties of the as-built parts of four materials. During LPBF forming, the melts developed from continuous and semicylindrical to discontinuous and “medicine spoon”-shaped at low and high linear energy densities (LEDs), respectively. The Ti6Al4V powder bed exhibited a long trailing melt pool and acted deeper (i.e., keyhole mode). The AlSi10Mg powder bed exhibited a smaller melt pool and did not exhibit trailing (i.e., heat-transfer mode). For Inconel 718 alloy and AlSi10Mg alloy, the improvement of mechanical properties is due to the precipitation of nanoparticle phase. The equilibrium of α+β phase results in the ideal strength and plasticity of Ti6Al4V alloy. The gradual disappearance of the cellular substructure reduces the strength of 304 stainless steel, but increases the plasticity. Process parameters correlate simulations with experiments and establish a "process-structure-properties" system. This study provides insights into melt evolution and flow behavior and is a reference for selecting and optimizing materials, laser-process parameters, and heat treatment regimes in practical engineering.

Insight into internal oxidation mechanism of hot rolled Si–Mn added high strength steel: Pure iron layer formation

In order to reveal special morphology formation mechanism of surface continuous Fe layer, through the vacuum sealing heat treatment experiment, the scale transformation process and the mechanism of oxygen pressure reduction in the coiling process of hot rolled steel are obtained. After discussion, it is considered that the surface pure Fe produced by heat treatment under the condition of vacuum sealing of C–Mn–Si steel sheet is due to the internal oxidation of Mn and Si in the substrate and decarburization reaction, and finally lead to the decomposition of oxide scale, resulting in the special structure of surface pure Fe, intermediate oxide scale and internal oxidation.

Parametric study on conductive patterns by low-temperature sintering of micron silver ink.

The fabrication of dense conductive patterns was achieved by low-temperature sintering of 1-3 μm micron silver flakes. A small amount of 20-50 nm nanosilver particles were added in the gaps of the micron silver flakes. The effects of sintering temperature, holding time and heating rate on the morphological evolution and formation mechanism of the sintered silver pattern were investigated in detail. Interestingly, rapid sintering (RS) can be achieved by removing the heating process from 70 °C up to the sintering temperature. The electrical resistivity of the sintered silver patterns was 10.8 × 10-6 Ω cm at 140 °C for 30 min under a pressure of 10 MPa. Moreover, the electrical resistivity of the sintered silver pattern for RS for 20 min does not change significantly after 6000 bending cycles. This work provides a new method to fabricate conductive patterns using micron silver flakes with the purpose of promoting the application of silver inks.

TC4 Titanium Alloy Track Morphology and Pore Formation Mechanism in Laser Powder Bed Fusion Process

TC4 Titanium Alloy Track Morphology and Pore Formation Mechanism in Laser Powder Bed Fusion Process

Molecular dynamics simulation on crystal defects of single-crystal silicon during elliptical vibration cutting

In recent years, elliptical vibration cutting (EVC) has become a promising technique to fabricate high quality surface of single-crystal silicon. However, our understanding for its cutting mechanism, especially the evolution of the crystal defects in subsurface workpiece is insufficient. In this paper, molecular dynamics simulation was carried out to explore the formation mechanism of crystal defects in single-crystal silicon during EVC. A three-dimensional MD model was adopted to demonstrate the interaction between subsurface damage and tool movement in one vibration cycle. The results indicate that the formation mechanism of surface morphology including elastic recovery and side flow is greatly determined by the cutting stage in EVC. Meanwhile, the preferred slip motion during subsurface damage formation is distinct in the extrusion and shear stage. Furthermore, the influence of cutting temperature and speed on the formation of crystal defects was investigated. It is found that at elevated temperature, the proportion of the Shockley partial dislocations are apparently increased, and recrystallization process is apparently promoted on the interface of the distorted/crystal region. As the speed ratio increases, the generation and propagation of the crystal defects are suppressed, which is advantageous for suppressing the subsurface damage. These findings provide a comprehensive theoretical basis for improving the understanding in the formation mechanism of crystal defects of single-crystal silicon in EVC.

Fabrication of oxide-free dimple structure on germanium via electrochemical jet machining enhanced by opposing laser irradiation

The electrochemical machining (ECM) of germanium (Ge) wafer can be significantly improved in terms of efficiency and localization by introducing laser irradiation. However, residual oxide particles usually exist when using neutral electrolyte. In this study, the NaNO3 electrolyte jet is formed via a cathodic nozzle and impacts perpendicularly on the bottom of the Ge wafer, at which position the nanosecond (ns) laser irradiates from opposing side to locally and precisely enhance the electrical conductivity. In this way, the dimple structure without any detectable oxidation products can be efficiently fabricated. Characterization of surface morphology is then amply conducted. The radial lines consisting of regular micro-waving structure are usually noticeable, especially near the dimple edge, which may be attributed to the rapid and radial electrolyte flow along the concave sidewall. In contrast, irregular corrugated pattern can be observed near the dimple center, which may be caused by the electrolyte turbulence after impingement. In addition, parametric experimental study has been carried out, and the effects of the applied voltage, laser power and electrolyte concentration on the dimple profile and surface characteristics have been respectively detailed discussed. Finally, simulation study of the electrolyte flow field is conducted to reveal the distribution regularities of velocity and pressure, to deepen the understanding of formation mechanism of the complex surface morphology.

A facile one-step gel process for precipitation of multifractal NaCl crystals and morphology evolution from sodium silicate gel

• Crystallization of NaCl in colloidal-salt system by a one-step gelation process. • Varying the pretreatment and gel conditions synthesizes DLA and dendrite patterns. • XRD analysis explains the dendrite pattern with distinct preferred orientation. • <110> and <111> directions determine the three- and four-fold symmetry dendrites. • Higher gelation degree contributes to precipitate regular fractal dendrite. In the colloidal-salt system of sodium silicate and sodium chloride, three-fold and four-fold symmetric dendrites and diffusion-limited aggregation (DLA) of sodium chloride crystals have been synthesized by a simple one-step gelation process without changing the solution composition. The morphology variation is realized by changing the sol pretreatment and gelation process’s heating mode. And the gelation degree of sodium silicate and the anisotropy of crystal growth is the morphology formation mechanism. Four-fold symmetric dendrites are related to preferential growth in the <110> direction, while three-fold symmetric dendrites are due to preferential orientation changes from <111> to <100> and then to <111>. EDS composition analysis showed that the high gelling degree is more accessible to precipitate regular fractal dendrites with preferred orientation.

The formation mechanism of microcracks and fracture morphology of wood during drying

The surface checks or internal cracks from drying could significantly affect the processing and utilization of the wood. Therefore, it is of great significance to investigate the formation mechanism of cracks and reduce its occurrence. In this work, the development of cracking was quantified and its relationship with moisture content (MC) gradient and anisotropic shrinkage was analyzed. Results showed that the slight shrinkage occurred at the MC of 40%, and the shrinkage ratio at the end of drying was about 7.38% in the tangential (T) direction and 4.35% in the radial (R) direction. The shrinkage ratio of T/R in the MC range of 30%–15% was about 1.8, which was higher than that (1.65) in the MC range of 15%–5%. Cracks initiation was observed at average MC of 45%. The area and number of cracks reached a maximum at 15% MC. During the late stage of drying, the drying stress of the surface layer was reversed from tensile to compressive, which leads to the narrowing or closure of the cracks. Moreover, the fracture morphology of wood cells was observed at the microscopic level, indicating that the failure firstly occurred in the intercellular layer between the ray tissue and the tracheid in the latewood. The ray cells presented intact, and the lamellar structure between ray tissues and between the ray cells and the tracheids were the weak points of wood during drying. The results would contribute to keeping in minimum drying defects and improving the drying quality of wood.

Synthesis of Dimpled Particles by Seeded Emulsion Polymerization and Their Application in Superhydrophobic Coatings.

Dimpled particles are synthesized through the seeded polymerization of fluoroacrylate and styrene on swelled polystyrene spheres. The morphologies of the particles can be controlled by the polymerization temperature, the amount of solvent swelling the seeds or the ratio of the fluoroacrylate monomer over styrene. Golf-ball-like particles with many small dimples on their surfaces are obtained at low polymerization temperatures or with a small amount of solvent. Particles with a large single dimple are formed at higher polymerization temperatures, with larger solvent amounts or a higher ratio of fluoroacrylate over styrene. The morphology formation mechanism of these dimpled particles is proposed and the application of these particles in the fabrication of superhydrophobic coatings is demonstrated.

Recent progress on low-cost ceramic membrane for water and wastewater treatment

Great progress in the development of low-cost ceramic membranes from alternative materials have been achieved recently towards various application especially water and wastewater treatment. However, their significance has not been fully recognized and understood especially in term of their microstructural analysis such as formation of grain growth and microcracks. This review paper summarizes fabrication method, alternative materials, microstructure, wettability, mechanical properties and application of low-cost ceramic membrane. The fabrication method including slip casting, tape casting, extrusion, pressing method and phase inversion technique are described. Alternative materials used in low-cost ceramic membrane fabrication are discussed and categorized into clays, agricultural waste, industrial waste and animal bone waste. The mechanisms of morphology formation, microstructure and wettability properties are analysed. Modification strategies for the surface of low-cost ceramic membrane are discussed, and classified into modification for separation application, modification for photocatalytic application and modification for membrane distillation and membrane contactor system. Modification improves the membrane structure by changing the pore size, porosity and wettability properties of low-cost ceramic membranes. Mechanical properties of low-cost ceramic membranes are also discussed in detail towards several mechanism, like grain growth phenomenon and formation of microcracks which also considered as membrane defects. Grain growth phenomenon can be divided into normal and abnormal grain growth. Meanwhile, formation of microcracks could be occurred in single-phase polycrystalline ceramics that have anisotropic grains or biphasic polycrystalline grains. The application of low-cost ceramic membrane in seawater desalination, oily wastewater treatment, heavy metal adsorption, textile separation and photocatalytic application are reviewed. Finally, some possible opportunities and challenges for further development of low-cost ceramic membrane are pointed out.

Morphological characteristics and formation mechanism of latent scratches in chemical mechanical polishing

Latent scratches are extremely shallow scratches inevitably introduced during chemical mechanical polishing (CMP), which deteriorates the performance of functional crystals. Although latent scratches can currently be detected by some advanced microscopes, there is still a lack of in-depth understanding of them. In this paper, we describe the morphological characteristics of latent scratches using atomic force microscopy and develop a mathematical model to explain the formation mechanism of latent scratches with YAG crystals as an example. The observations showed that the distributions of the depth and width of latent scratches were always Gaussian-like. And the pressure was positively correlated with the number of latent scratches but did not significantly affect the depth and width. The proposed mathematical model describes the contact state between the particles and the crystal surface, and identifies the formation of latent scratches resulting from plastic deformation of the crystal surface, a conclusion further supported by transmission electron microscopy observations. The model also explains that the distribution of depth and width is mainly determined by the material properties and that pressure affects the number of particles in contact with the workpiece but does not significantly change the contact stress between individual particles and the workpiece. There is an upper limit to the contact stress, resulting in scratches always below 1 nm in depth. The analysis of latent scratches is of great significance to removing latent scratches and manufacturing the ultra-smooth surface in the CMP process.

Research on the formation mechanism of surface morphology in three-excitation ultrasonic spatial vibration-assisted turning

To improve the machining performance of different processing materials, a three-excitation ultrasonic spatial vibration-assisted turning system is proposed, which realizes the non-unity of the plane where the cutting trajectory of the tool is located. The influence and formation law of three-excitation ultrasonic spatial vibration-assisted turning on the surface roughness of the workpiece under different vibration parameters (amplitude) and machining parameters (cutting speed, cutting depth, and feed) were analyzed by response surface methodology. The results show that in terms of vibration parameters, the influence of ultrasonic vibration applied in the horizontal direction on surface roughness is significantly greater than that of ultrasonic vibration applied in the vertical direction, while the feed has the greatest influence on surface roughness, followed by cutting speed. The surface roughness of common turning, one-dimensional ultrasonic vibration-assisted turning, ultrasonic elliptical vibration-assisted turning, and three-excitation ultrasonic spatial vibration-assisted turning was theoretically analyzed and experimentally compared. The results show that compared with the other three turning methods, the three-excitation ultrasonic spatial vibration-assisted turning can obtain a lower surface roughness and have good machinability.

Morphological Distribution and Formation Mechanisms of Antimony in the Shallow Groundwater of the Xikuangshan Antimony Mine in Hunan, China

The century-old mining development and utilization of antimony (Sb) ore in Xikuangshan (XKS) mine, groundwater antimony pollution has attracted great attention. At present, the sources and geochemical behaviors of high Sb groundwater in this area have been widely recognized, but morphological distribution and formation mechanisms of Sb(V) and Sb(III) in shallow groundwater were still little known. Forty-three groundwater samples of Magunao aquifer (D3x4) were collected between June and September 2020 to determine morphological distribution and formation mechanisms of Sb valence state in the recharge area, runoff area and discharge area. The range of Sb content in the recharge area, runoff area, and discharge area of the D3x4 water was 3.300 × 10−3–7.982 mg/L, 1.760 × 10−2–17.326 mg/L and 1.230 × 10−2–16.773 mg/L, respectively. The D3x4 water is dominated by Sb(V), which form was Sb(OH)6−. The Sb(V) mainly comes from the oxidative dissolution of Sb2S3, the mining activities, and the leaching of arsenic alkali residues. The silicate mineral weathering, carbonate mineral dissolution, and ion exchange promote the dissolution of Sb2S3. At the same time, redox and competitive adsorption in the runoff area increase the Sb(V) content in the water environment. The results of this research provide an understanding of the mechanism of Sb pollution in shallow groundwater and will help in controlling water-environment pollution and securing water-resource in mining areas.

Microscale formation mechanism of surface morphology and chips features of granitic rocks considering different machining parameters

Microscale formation mechanism of surface morphology and chips features of granitic rocks considering different machining parameters

Simulation and experimental investigation of the surface morphology formation mechanism of a D-shaped fiber processed using a pulsed CO2 laser

Traditional D-shaped optical fibers are manufactured using mechanical polishing or chemical corrosion techniques, which inevitably introduce sub-surface defects or impurities. In this study, a new D-shaped optical fiber manufacturing method using CO2 laser ablation technology is proposed. Laser ablation technology is a complex multi-physical coupling process involving phase changes. To fully understand the surface morphology formation mechanism during CO2 pulsed laser processing, a three-dimensional numerical model and experimental analyses were used to elucidate the relationship between the fiber surface temperature distribution, surface morphology evolution, processing quality, processing efficiency, and laser parameters. The simulation results showed that the residual temperature between laser pulses was lower than the structural transition temperature of the material, and the simulated morphology was consistent with the experimental results. Moreover, the overlapping spot energy resulted in the processed surface exhibiting a periodic ripple structure. The ablation depth was proportional to the pulse width and inversely proportional to the scanning speed. In addition, different laser pulse widths had almost no effect on the roughness and flatness of the processed surface, but the laser scanning speed had a significant impact on both indexes. These results can guide the optimization of CO2 laser processing methods.

The Impact of Benzothiadiazole on the Optoelectronic Performance of Polymer/PC71BM Blend Films and Their Application in NIR Phototransistors

AbstractD‐A conjugated polymers P1 and P2 are synthesized by copolymerizing bisthiophene‐fused diketopyrrolopyrrole (4,11‐bis(2‐decyltetradecyl)‐7H,14H‐thieno[3',2':7,8]‐indolizino[2,1‐a]thieno[3,2‐g]indolizine‐7,14‐dione, BTI) with terthiophene and thiophene‐benzothiadiazole‐thiophene, respectively. Molecular packing is characterized by X‐ray diffraction. The film morphology is characterized by atomic force and scanning electron microscopy. The vertical phase separation is characterized by XPS. The mechanism of film morphology formation is explained from intermolecular interaction, kinetics, and surface free energy. The spin‐coated films of polymers blended with PC71BM are served as semiconductor layers in near‐infrared (NIR) phototransistors. The impact of morphology on optoelectronic performance is analyzed. The mobility of organic field effect transistors based on P1 or P2 thin films remains constant with the addition of PC71BM with weight ratio being less than 50%. The main reason is that π–π stacking in both P1 and P2 thin films is at all directions and PC71BM does not disturb the charge percolation path. Benzothiadiazole in P2 enables stronger mutual attraction between P2 and PC71BM, and therefore large contact area between P2 and PC71BM forms in the heterojunction. The photoresponsivity improves by 2 times for NIR phototransistors based on P2/PC71BM when decreasing light intensity from 63 to 1.8 µW cm‐2. The above results suggest a feasible conjugated polymer design rule for high sensitivity NIR phototransistors.

Tailoring Ordered Wrinkle Arrays for Tunable Surface Performances by Template-Modulated Gradient Films.

Complex wrinkled microstructures are ubiquitous in natural systems and living bodies. Although homogeneous wrinkles in film-substrate bilayers have been extensively investigated in the past 2 decades, tailoring heterogeneous wrinkles by a facile method is still a challenge. Here, we report on the controllable heterogeneous wrinkles in template-modulated thickness-gradient metal films sputter-deposited on polydimethylsiloxane substrates. It is found that the stress of the gradient film is strongly position-dependent and the wrinkles are always restricted in thinner film regions. The morphological characteristic and formation mechanism of the heterogeneous wrinkles are analyzed and discussed in detail based on the stress theory. Ordered wrinkle arrays are achieved by adjusting the deposition time, copper grid period, template shape, and lifting height. The surface performances (e.g., the friction property) are well controlled by the wrinkle arrays. This work could promote better understanding of the spontaneously heterogeneous wrinkles in template-modulated gradient films and controllable fabrication of various wrinkle arrays by independently tuning film deposition conditions and template parameters.

KrF excimer laser induced damage and its mechanism of CaF2 single crystal with (1 1 1), (1 1 0) and (1 0 0) planes

CaF2 crystal generally has a fluorite-type crystal structure, in which the cleavage plane is {111} and the slip system is {100} 〈110〉. The mechanical properties of different crystal planes are obviously different. In this investigation, 248 nm KrF excimer laser damage experiments were carried out on three different crystal planes (100), (110) and (111) of CaF2 crystals. The laser induced damage threshold was obtained, and the relationship between crystal plane and damage characteristics was analyzed. Our work highlights were that by analyzing the relationship among crystal plane, cleavage plane and slip plane, the formation mechanism of surface morphology of (111), (110) and (100) crystal planes were summarized.