Small Surface Roughness Research Articles

WASPAS Optimization in Advanced Manufacturing

This paper presented optimization of machining parameters for high pressure abrasive water jet (AWJ) cutting of Hardox 500 steel utilizing WASPAS approach. Weighted aggregated sum product assessment (WASPAS) method is explored as an effective MCDM tool while solving advanced manufacturing decision making problems. It is a unique combination of two well-known MCDM approaches, i.e. weighted sum model (WSM) and weighted product model (WPM).The tests were caried out according to the orthogonal matrix (Taguchi) L27. The control parameters of process such pressure, abrasive flow rate and traverse speed was optimized under multi-response conditions namely cutting depth and surface roughness. The optimal set of control parameters was established on the ground of the overall weighted criterium. Effects shows that optimal set for high cutting depth and small surface roughness are high pressure, high abrasive flow rate and small traverse speed. Results of research have shown that machining efficiency at keeping satisfactory level quality of cut surface can be improved this approach.

Performance of trans perovskite solar cells improved by finely adjusting the particle size of nickel oxide nanoparticles through pH value

As a low-cost, high stable hole transport material, nickel oxide has been widely used in inverted structure perovskite solar cells in recent years. By far, the most common method of preparing nickel oxide hole transport layers is spin-coating pre-prepared nickel oxide nanoparticles (NiO<sub><i>x</i></sub> NPs), which puts forward high requirement for the particle sizes and solution processing capabilities of NiO<sub><i>x</i></sub> NPs. In this work, the sizes of NiO<sub><i>x</i></sub> NPs are precisely controlled by adjusting the pH value of the system in the synthesis process, and high-quality nickel oxide hole transport layers are then prepared. The experimental results exhibit that the NiO<i>x</i> NPs with sizes of 5–10 nm are obtained at a pH value in a range of 9.5–9.8. More interestingly, the obtained NiO<sub><i>x</i></sub> NPs have good dispersion stability and can achieve long-term dispersion in aqueous solution. Furthermore, the structural composition analysis of NiO<sub><i>x</i></sub> NPs shows that the pH value of the synthesis system does not have a significant effect on the material structure nor composition of the NiO<sub><i>x</i></sub> NP. Surface morphological analysis shows that the NiO<sub><i>x</i></sub> film prepared by the pH-controlled NiO<sub><i>x</i></sub> NPs is rather dense and particularly flat with small surface roughness. It is also found that the film exhibits good hole extraction capability. We also fabricate an inverted perovskite solar cell based on the NiO<sub><i>x</i></sub> film. The device structure is ITO/NiO<sub><i>x</i></sub>/CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub>/PC61BM/Bphen/Ag. It yields a good photovoltaic conversion efficiency (17.39%). In addition, the device is almost hysteresis-free. Our experimental results exhibit that the performance of perovskite solar cells can be effectively improved by precisely controlling the sizes of NiO<sub><i>x</i></sub> NPs through pH values. Our work is expected to facilitate the development of NiO<sub><i>x</i></sub>-based perovskite solar cells.

Performance of trans perovskite solar cells improved by finely adjusting the particle size of nickel oxide nanoparticles through pH value

As a low-cost, high stable hole transport material, nickel oxide has been widely used in inverted structure perovskite solar cells in recent years. By far, the most common method of preparing nickel oxide hole transport layers is spin-coating pre-prepared nickel oxide nanoparticles (NiO<sub><i>x</i></sub> NPs), which puts forward high requirement for the particle sizes and solution processing capabilities of NiO<sub><i>x</i></sub> NPs. In this work, the sizes of NiO<sub><i>x</i></sub> NPs are precisely controlled by adjusting the pH value of the system in the synthesis process, and high-quality nickel oxide hole transport layers are then prepared. The experimental results exhibit that the NiO<i><sub>x</sub></i> NPs with sizes of 5–10 nm are obtained at a pH value in a range of 9.5–9.8. More interestingly, the obtained NiO<sub><i>x</i></sub> NPs have good dispersion stability and can achieve long-term dispersion in aqueous solution. Furthermore, the structural composition analysis of NiO<sub><i>x</i></sub> NPs shows that the pH value of the synthesis system does not have a significant effect on the material structure nor composition of the NiO<sub><i>x</i></sub> NP. Surface morphological analysis shows that the NiO<sub><i>x</i></sub> film prepared by the pH-controlled NiO<sub><i>x</i></sub> NPs is rather dense and particularly flat with small surface roughness. It is also found that the film exhibits good hole extraction capability. We also fabricate an inverted perovskite solar cell based on the NiO<sub><i>x</i></sub> film. The device structure is ITO/NiO<sub><i>x</i></sub>/CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub>/PC<sub>61</sub>BM/Bphen/Ag. It yields a good photovoltaic conversion efficiency (17.39%). In addition, the device is almost hysteresis-free. Our experimental results exhibit that the performance of perovskite solar cells can be effectively improved by precisely controlling the sizes of NiO<sub><i>x</i></sub> NPs through pH values. Our work is expected to facilitate the development of NiO<sub><i>x</i></sub>-based perovskite solar cells.

Self-sharpening property of porous metal-bonded aggregated cBN wheels during the grinding of Ti–6Al–4V alloys

Grinding process with cubic boron nitride (cBN) superabrasive wheels has been the subject of extensive research during high efficiency and precision machining difficult-to-cut materials in aerospace and aviation industries. However, the grinding performance and tool-life of conventional cBN abrasive wheels are severely affected by the probable macro-fracture and pull-out of cBN grains owing to their anisotropic crystalline structure. In this case, porous metal-bonded grinding wheels coupled with high-performance aggregated cBN abrasive grains were developed to improve tool performance and machined surface integrity. Characterisation of morphologies, including as-sintered aggregated cBN abrasive grains, pore structures and grain wear evolutions, was performed. The grinding ratio, grinding forces, force ratio and ground surface roughness were evaluated through single-grain grinding of Ti–6Al–4V alloys. Experimental results indicated that the porous aggregated cBN wheels had abundant chip storage space and excellent wear resistance. A stable grinding force ratio and small ground surface roughness were obtained during the tool wear tests due to the combined characteristics of microfracture and partial macrofracture of multi-layer cBN particles.

Numerical simulation of surface roughness effects on the vortex-induced vibration of a circular cylinder at a subcritical Reynolds number

The Vortex-Induced Vibration (VIV) of a circular cylinder with different surface roughness is numerically simulated at a subcritical Reynolds number of 3900. The effects of surface roughness on the vibration response amplitude, hydrodynamic coefficients and wake vortex are analyzed. The results show that as surface roughness increases, four branches (initial, upper, super-upper and lower branches) appear in the VIV response for a smooth cylinder, and for a cylinder with a small surface roughness of K S / D = 2.5 × 10 − 3 , this response changes to three branches (initial, upper and lower branches). The vortex shedding for the initial and lower branches is 2S mode, and that for the upper and super-upper branches (lock-in range) is P + S − , P+S + and 2P modes. With increasing surface roughness, the maximum amplitude has little difference, and the width of the lock-in range increases. A large jump in the vortex phase at the transition of the initial and upper branches and a large jump in the total lift phase at the transition of the upper and lower branches are found, and these jumps are associated with a switch in the timing of vortex shedding (jump of the vortex phase: 2S mode to P + S − mode; jump of the lift phase: other modes to 2S mode). The results are significant for the development of flow and vibration control technology.

Multi-criteria decision making under the MARCOS method and the weighting methods: applied to milling, grinding and turning processes

The efficiency of cutting machining methods is generally evaluated through many parameters such as surface roughness, material removal rate, cutting force, etc. A machining process is considered highly efficient when it meets the requirements for these parameters, such as ensuring small surface roughness, high material removal rate, or small cutting force, etc. However, for each specific machining condition, sometimes the objective functions give contradictory requirements. In this case, it is necessary to implement multi-criteria decision making, i.e., make a decision to ensure harmonization of all required objectives. In this paper, a multi-criteria decision-making study is presented for three common machining methods: milling, grinding, and turning. In each machining method, the weights of the criteria were determined by four different methods, including Equal weight, ROC weight, RS weight and Entropy weight. The MARCOS method was applied for multi-criteria decision making. The best alternative was found to be the same as the weights were determined using the Equal weight and Entropy weight methods. In the remaining two weighting methods, the best alternative found depends on the order where the criteria were arranged, not these methods themselves. Direction for further research has been suggested in this study as well.

Determination of band alignment between GaO x and boron doped diamond for a selective-area-doped termination structure

An n-GaO x thin film is deposited on a single-crystal boron-doped diamond by RF magnetron sputtering to form the pn heterojunction. The n-GaO x thin film presents a small surface roughness and a large optical band gap of 4.85 eV. In addition, the band alignment is measured using x-ray photoelectron spectroscopy to evaluate the heterojunction properties. The GaO x /diamond heterojunction shows a type-II staggered band configuration, where the valence and conduction band offsets are 1.28 eV and 1.93 eV, respectively. These results confirm the feasibility of the use of n-GaO x as a termination structure for diamond power devices.

Voltage Control of Perpendicular Magnetic Anisotropy in Multiferroic Composite Thin Films under Strong Electric Fields.

"Ferroelectric/ferromagnetic" multiferroic composites with perpendicular magnetic anisotropy (PMA) are useful for developing power-efficient magnetic memories. Voltage control of PMA has been demonstrated in bulk multiferroic composites based on ferroelectric single crystals, but they are not compatible for integration. Multiferroic composite thin films are useful for developing integrated devices; however, voltage control of PMA in them has not been achieved yet at room temperature due to their low magnetoelectric (ME) coupling coefficient. Here, we demonstrate such functionality and propose to enhance their ME coupling effect under a strong electric field by taking full advantage of the large dielectric strength of ferroelectric thin films. First, the thickness-dependent breakdown of Pb(Zr0.384Ti0.576Nb0.04)O3 (PNZT) thin films was studied, and the two-layer (∼200 nm) samples exhibited the highest breakdown strength (3.68 MV/cm) and small surface roughness (<1 nm). Second, we fabricated "PNZT/(Co/Pt)5" thin films with strong PMA whose breakdown strength is nearly independent of the top electrode materials. Finally, voltage-induced effective magnetic field (Heff) in "PNZT/(Co/Pt)5" was studied. It is comparable to that achieved in bulk composites and will induce magnetization switching under strong electric fields. Multiferroic composite thin films with large breakdown strength will provide a useful platform for enabling integrated multiferroic devices.

Characterization and formation mechanisms of rail chips from facing grinding by abrasive wheel

Rail grinding is a widely-used method to eliminate surface damages on railway tracks. The grinding chips are closely related to the grinding parameters and the grinding quality. Therefore, the investigation on the characteristics and the formation mechanism of chips from rail grinding is beneficial for the optimization of rail grinding process. In the present study, the grinding chips from the real rail grinding in the field and from the rail grinding experiments in the laboratory were analyzed in terms of their morphologies, microstructural evolution and chemical characteristics. The results showed that flowing, knife, slice and spherical chips were generated during rail grinding. The formation mechanism of flowing, knife and slice chips was plastic deformation by forces from abrasive grains with oxidation in air by grinding heat. Primary and secondary shear zones and central zones were generated. In the primary shear zone, cracks were generated in knife and slice chips. In the secondary shear zone, obvious plastic deformation was formed in knife and slice chips and a significant white etching layer (WEL) was generated in knife chips. The formation mechanism of spherical chips was melting of small powdery grinding debris by the high temperature and the subsequent solidification, accompanied with severe oxidization in air. The oxides produced in chips consisted of FeO, Fe3O4, Fe2O3 and AlFe2O4. The grinding quality could be predicted through observing the grinding debris. The larger percentage of flowing chips represented the better grinding quality (smaller surface roughness, slighter surface burn and thinner WEL on ground rail), which could be the goal for the grinding parameters choice.

Surface Integrity and Corrosion Resistance of 42CrMo4 High-Strength Steel Strengthened by Hard Turning.

To improve the surface corrosion resistance of 42CrMo4 high-strength steel used in a marine environment, this article studied the effects of hard turning on the surface integrity and corrosion resistance of 42CrMo4 high-strength steel through the single factor experimental method, namely hard turning, polarization corrosion, electrochemical impedance spectroscopy, potentiodynamic polarization curve, and salt spray tests. The results indicated that the surface integrity was modified by the hard turning, with a surface roughness lower than Ra 0.8 μm, decreased surface microhardness, fine and uniform surface microstructure, and dominant surface residual compressive stress. The hard turning process was feasible to strengthen the surface corrosion resistance of 42CrMo4 high-strength steel. The better corrosion resistance of the surface layer than that of the substrate material can be ascribed to the uniform carbides and compact microstructure. The corrosion resistance varied with cutting speeds as a result of the changed surface microhardness and residual compressive stress, varied with feed rates as a result of the changed surface roughness, and varied with cutting depths as a result of the changed surface residual compressive stress, respectively. The surface integrity with smaller surface roughness and microhardness and bigger surface residual compressive stress was beneficial for corrosion resistance.

A Fuzzy Evaluation of Tool Materials in the Turning of Marine Steels

To recommend one suitable tool material for the cutting of marine steels under special conditions and requirements in emergency rescues of capsized steel ships, the cermet tools, cemented carbide tools and coated carbide tools were evaluated using a fuzzy evaluation method concerning cutting force, cutting temperature, surface roughness and tool wear. Experimental results indicate that the tool cutting performance was diverse and difficult to evaluate with a single evaluation index. The cemented carbide tools presented bad cutting performance with severe wear. Compared with the cemented carbide tools, the cermet tools showed excellent wear resistance with about 60.3% smaller tool flank wear value and good surface quality with about 46.8% smaller surface roughness. The coated carbide tools presented low cutting temperatures about 15.6% smaller than those of the cermet tools. The result of fuzzy evaluation demonstrates that the cermet tools presented the best cutting performance, followed by the coated carbide tools, and then the cemented carbide tools. The cermet tools are recommended to cut marine steels in emergency rescues of capsized steel ships.

Indium-Based Micro-Bump Array Fabrication Technology with Added Pre-Reflow Wet Etching and Annealing.

Indium-based micro-bump arrays, among other things, are used for the bonding of infrared photodetectors and focal plane arrays. In this paper, several aspects of the fabrication technology of micrometer-sized indium bumps with a smooth surface morphology were investigated. The thermal evaporation of indium has been optimized to achieve ~8 μm-thick layers with a small surface roughness of Ra = 11 nm, indicating a high packing density of atoms. This ensures bump uniformity across the sample, as well as prevents oxidation inside the In columns prior to the reflow. A series of experiments to optimize indium bump fabrication technology, including a shear test of single columns, is described. A reliable, repeatable, simple, and quick approach was developed with the pre-etching of indium columns in a 10% HCl solution preceded by annealing at 120 °C in N2.

Dimensionality induced enhancement of ferromagnetic spin order and ferroelectric polarization in Ga doped α-Fe2O3 thin films

The thin films of Ga doped hematite (α-Fe2O3) were grown on p-Si 〈111〉 substrate using Pulsed Laser Deposition technique. The as-grown films indicated crystalline peaks of rhombohedral structure. The films exhibited enhancement of ferromagnetic properties. The reduction of dimensionality of the materials in thin films (2D) has shown unusual magnetic spin order and exchange bias effect at temperatures < 70 K. The ferromagnetic parameters (magnetization, coercivity) showed dependence on composition, deposition conditions and heat treatment of the films. The as-grown films showed a good signature of ferroelectric polarization. The as-grown films of Fe1.8Ga0.2O3, having relatively large surface roughness, exhibited smaller magnetic moment in comparison to as-grown films of Fe1.6Ga0.4O3 with small surface roughness. The X-ray photoelectron spectroscopy measurements confirmed a chemically homogeneous state of high spin Fe3+ ions in as-grown films of Fe1.6Ga0.4O3 composition, whereas chemical state of Fe ions is consisting of the mixture of high spin Fe3+ and Fe2+ states in as-grown films of Fe1.8Ga0.2O3.

Parameter Selection to Ensure Multi-Criteria Optimization of the Taguchi Method Combined with the Data Envelopment Analysis-based Ranking Method when Milling SCM440 Steel

SCM440 steel is a commonly used material for making plastic injection molds and components such as gears, transmission shafts, rolling pins, etc. Surface roughness has a direct influence on the workability and durability of the parts and/or components, while the Material Removal Rate (MRR) is a parameter that is used to evaluate the productivity of the machining process. Furnished products with small surface roughness and large MRR is the desired result by all milling processes. In this paper, the determination of the values of input parameters is studied in order to ensure that during the process of milling SCM440 steel, it will have the smallest surface roughness and the largest MRR. There are five parameters that are required to be determined, namely the cutting insert material, the tool nose radius, the cutting speed, the feed rate, and the cutting depth. The Taguchi method was applied to design the experimental matrix with a total of 27 experiments. Result analysis determined the influence of the input parameters on surface roughness and MRR. The Data Envelopment Analysis-based Ranking (DEAR) method was applied to determine the optimal value of the input parameters, which were used to conduct the milling experiments to re-evaluate their suitability.

Experimental study and theoretical modeling of coating-speed-dependent optical properties of TiO2-graphene-oxide thin films

Nanostructured titanium dioxide–graphene oxide (TiO2-GO) thin films have been successfully synthesized and deposited on glass substrates using spin coating technique. TiO2-GO nanocomposites were prepared using Titanium Tetra Isopropoxide (TIP) and Graphene Oxide (GO) nanosheets. The influences of spin coating deposition speed on the structural, morphological, and optical features of the resulting TiO2-GO samples have been investigated. X-ray diffraction (XRD) patterns showed an amorphous structure of all deposited films. Scanning electron microscopy (SEM) images demonstrated that these films are homogeneous and all free from cracking over the entire surface of the sample, regardless of the number of rotations used. Atomic force microscopy (AFM) topography images reveal that all samples are smooth with very small surface roughness. Optical data obtained from UV–Vis spectrophotometer measurement together with theoretical modeling using Tauc–Lorentz (TL) oscillator model showed that all films display high transmittance level around 85% from the visible to the near-infrared region. It is also shown that an increase in spin coating speed results in a decrease in the film thickness and the optical band gap. The observed optical features reveal that TiO2-GO thin films are promising candidate that can be used as transparent conducting oxide electrode in solar cells.

Different Morphology Dependence for Efficient Indoor Organic Photovoltaics: The Role of the Leakage Current and Recombination Losses.

Efficient indoor organic photovoltaics (OPVs) have attracted strong attention for their application in indoor electronic devices. However, the route to optimal photoactive film morphology toward high-performance indoor devices has remained obscure. The leakage current dominated by morphology exerts distinguishing influence on the performance under different illuminations. We have demonstrated that morphology reoptimization plays an important role in indoor OPVs, and their optimal structural features are different from what we laid out for outdoor devices. For indoor OPVs, in order to facilitate low leakage current, it is essential to enhance the crystallinity, phase separation, and domain purity, as well as keeping small surface roughness of the active layer. Furthermore, considering the reduced bimolecular recombination at low light intensity, we have shown that PM6:M36-based indoor devices can work effectively with a large ratio of the donor and acceptor. Our work correlating structure-performance relation and the route to optimal morphology outlines the control over device leakage current and recombination losses boosting the progress of efficient indoor OPVs.

Optimization of electrical discharge machining processing for ceramics using grey-taguchi system

Electrical discharge machining (EDM) is one of the importantly non-traditional processing technologies employed for ceramics’ surface processing. Modeling and optimization of the EDM process are essentially applied to find and obtain the optimal values of the responses for materials having smaller surface roughness, higher removing rate of materials, lower electrode wear rate. In this study, the Grey-Taguchi system with AHP weighting was applied in order to optimize the multi-responses of the EDM processing for ceramics. When the EDM processing was used in the ZrO2 ceramics for adhesive metal foils, the multi-response gray relational grade for the optimal level of machining parameter was 0.2685, which was higher than those using the initial experimental conditions. This study has proven that using the Grey-Taguchi system method with AHP weighting to find a model with a highly efficient standard for optimizing differently advanced machining processes is profitable.

Effect of Sizing Agents on Surface Properties of Carbon Fibers and Interfacial Adhesion of Carbon Fiber/Bismaleimide Composites.

Physicochemical, surface, and mechanical properties of three batches of T800 grade carbon fibers (CFs) treated with three kinds of sizing agents and Toray T800H CFs were characterized to study the effect of sizing agents on surface properties. Scanning electron microscopy for morphology, atomic force microscopy calculations, and results for the content of sizing agents showed that sizing agent B improved the surface roughness and CFs with high content of sizing agent always presented small surface roughness in a certain content range 1.2–1.6%. Surface energy of CFs was calculated by Young’s contact angle using the test results with water and glycol, and contact angles with LY-1 and modified-AC531 were also acquired. The results proved that CFs of sizing agent group B had the highest average surface energy and the lowest average contact angles with both LY-1 and modified-AC531. From both single-filament and tensile strength test results, the average strength of CFs of sizing agent group B was found to be the lowest, which indicated that sizing agent B had an influence on tensile strength decrease of T800 grade CFs. Comparing the results of interfacial shear strength both in a natural dry state and after hygrothermal treatment, high surface energy was found to be the key element to obtain high interfacial adhesion between T800 grade CFs and bismaleimide, and high surface roughness and low contact angle also played important roles. Among sizing agents A, B, and C, A had an effect on the interfacial shear strength decrease of CFs in the natural dry state, while C had that after hygrothermal treatment.

The Influence of Different Slicer Software on 3d Printing Products Accuracy and Surface Roughness

Rapid Prototyping (RP) is a manufacturing process that produces a 3D model CAD to be a real product rapidly by using additive manufacturing technology. In this case, the product will print layer by layer uses a 3D printer machine. The 3D printer requires slicer software to convert CAD data into data that a 3D printer machine can read. Research is done to analyze the effect of three kinds of slicer software on 3D printing objects on the accuracy and surface roughness of the product. The 3D model CAD is sliced using three different slicer software, namely Ideamaker, Repetier Host, and Cura. The slice model result from each slicer will be printed on a 3D printer machine with the same process parameters to be compared. Then the product's dimensional and surface roughness will be measured to determine the effect of each slicer on product quality. The best quality of the product reflected the most suitable slicer software for the 3D printing machine that used. The best results achieved by Cura slicer because it has resulted in small dimensional deviations (max 0,0308±0,0079) and stabile high surface roughness of the product (max 1,585+059).

Micromachined W-band dual-band quasi-elliptic waveguide filter

This paper presents a W-band dual-band waveguide filter using SU-8 photoresist UV lithography technology. The filter has a parallel structure with both the bands of fourth-order quasi-elliptic responses by adopting easily manufactured coupling structures, enabling improved stopband rejection. The filter was designed to have two passbands centered at 80 GHz and 100 GHz and each band can be optimized independently without impact on the other. The fabricated prototype has small dimension errors and low surface roughness. Measured results show a good agreement with the simulated ones, with insertion losses for two passbands of 0.79 dB and 0.54 dB, return losses better than 10 dB, and fractional bandwidths of 7.2 % and 5.4 %. The experimental results are discussed and compared with the ones of similar structures using other machining techniques, confirming the feasibility of the design and fabrication methods of the filter.