Perfect Surface Research Articles

Kompozit Yama ile Tamir Edilmiş Oval Çentikli Çelik Plakanın Çekme Dayanımının Deneysel Olarak Araştırılması

In this study, the repairability of oval notched 304 austenitic stainless steel plate with carbon/epoxy composite patch was experimentally investigated. In this context, 250x40 mm test specimens were cut from 2 mm thick steel plate and in the CNC machine, oval notches 20x4 mm sized were opened in three diffrent directions on their centers. Carbon fiber reinforced composite patches were then prepared to patch these notches. The composites used in patches were produced by applying epoxy to triaxial fabrics by hand lay-up method and then hot pressing. Composite patches were cut from composite plates with water jet. These patches were then affixed with Weicon RK-7100 adhesive to one-sided and double-sided notched steel plates. Before the adhesion process, the dirt and residue layer on the surfaces of the plates were cleaned with a rotary felt. Then, by spraying solvent-based surface cleaner on the samples, a perfect adhesion surface was obtained. After the bonding process was completed, the samples were kept for three days in order for the adhesive to cure. When the samples were in their final form, static tensile tests were performed, tensile stresses were determined and comparisons were made on the graphics for each angle value without patches, one way patches and two way patches. It was found that the critical yield strength of the patched specimens was significantly improved comparaed to the unpatched samples. There was no sinificant difference between the patched and non-patched samples in the ultimate tensile strength.

Development of Models for Predicting Some Surface Responses in Oblique Metal Cutting Using Mild Steel and Coated Carbide

Oblique metal cutting is a milling process which constitutes the work piece, tool piece, machine centre and the machinist or operator. This research has been able to obtain some responses such as tool life, and the surface roughness. Most machine elements fail due to some poor surface finish errors such as craters, waviness, flay and lay. Previous researchers have focused more on the absolute value of the surface roughness (Ra) and this cannot provide for all the errors encountered on surface texture. The primary aim of this research is to develop models that can predict the surface roughness of machine parts produced in oblique metal cutting above the absolute value of the average surface roughness and in turn provide a document or framework for machinist which can serve as a guide for machinist. The work has been able to determine a near perfect surface roughness for mild steel using coated carbide as tool piece as the models developed has minimized the effect of surface roughness at run 6, 6 and 8 for Ra, Rz and maximized TL in the values of 1.071408 micrometer, 2.668293 micrometer and 49837238 seconds respectively. Also. the analysis of variance performed has also shown that is proper to accept the analysis using a significance ? level of 0.05.

Development of Models for Predicting Some Surface Responses in Oblique Metal Cutting Using Mild Steel and Coated Carbide

Oblique metal cutting is a milling process which constitutes the work piece, tool piece, machine centre and the machinist or operator. This research has been able to obtain some responses such as tool life, and the surface roughness. Most machine elements fail due to some poor surface finish errors such as craters, waviness, flay and lay. Previous researchers have focused more on the absolute value of the surface roughness (Ra) and this cannot provide for all the errors encountered on surface texture. The primary aim of this research is to develop models that can predict the surface roughness of machine parts produced in oblique metal cutting above the absolute value of the average surface roughness and in turn provide a document or framework for machinist which can serve as a guide for machinist. The work has been able to determine a near perfect surface roughness for mild steel using coated carbide as tool piece as the models developed has minimized the effect of surface roughness at run 6, 6 and 8 for Ra, Rz and maximized TL in the values of 1.071408 micrometer, 2.668293 micrometer and 49837238 seconds respectively. Also. the analysis of variance performed has also shown that is proper to accept the analysis using a significance α level of 0.05.

POINTS CLOUD PRE-PROCESSING AND SAMPLING BASED ON DISTANCE ALGORITHM TECHNIQUE

Although the rapid development of reverse engineering techniques such as a modern 3D laser scanners, but can’t use this techniques immediately to generate a perfect surface model for the scanned parts, due to the huge data, the noisy data which associated to the scanning process, and the accuracy limitation of some scanning devices, so, the present paper present a points cloud pre-processing and sampling algorithms have been proposed based on distance calculations and statistical considerations to simplify the row points cloud which obtained using MATTER and FORM 3D laser scanner as a manner to obtain the required geometrical features and mathematical representation from the row points cloud of the scanned object through detection, isolating, and deleting the noised points. A MATLAB program has been constructed for executing the proposed algorithms implemented using a suggested case study with non-uniform shape. The results were proved the validity of the introduced distance algorithms for pre-processing and sampling process where the proficiency percent for pre-processing was (18.65%) with a single attempt, and the counted deviation value rang with the sampling process was (0.0002-0.3497mm).

H2S Dissociation on Defective or Strained Fe (110) and Subsequent Formation of Iron Sulfides: A Density Functional Theory Study

In this paper, spin-polarized periodic density functional theory-based simulations were performed to investigate H2S adsorption and dissociation on the defective and strained Fe (110) surfaces which exist in real oil exploitation and transport. It was found that the defective surface facilitates H2S adsorption and dissociation with respect to the perfect surface, while the homogeneous external stresses, giving rise to uniform lattice expansion, show negligible effects for the strain estimated from experiment. More interestingly, the simulations predicted a correct order of phase transition at the Fe (110) surface by using the chemical potential based thermodynamic model, that is, from the elementary Fe crystal to the FeS crystal to the FeS2 crystal to the elementary S crystal with the S coverage on the Fe (110) surface increasing.

Ammonia deep chemical looping combustion on perfect and reduced Fe 2 O 3 : A theoretical account

Chemical looping combustion (CLC) between Fe2O3 and NH3 can lead to the generation of H2O, H2, NO, and N2 as the main product under different reaction stages, reasonable control of which can realize effective conversion and utilization of NH3. To initiate the CLC reaction, NH3 is chemically adsorbed on the perfect Fe2O3 surface with a hybrid between N and Fe, leading to the dehydrogenation of NH3 into *NH2 as the first reaction step. Then the second dehydrogenation step (*NH2→*NH) acts as the speed-control step for the oxidation of NH3 into H2O and N2, leading to the reduction of Fe2O3. The reduction of Fe2O3 promotes the further adsorption of NH3, especially the intermediate species *NH2, *NH, and *N, which favors the generation of H2O and N2. Further reduction of Fe2O3 into the oxidation state lower than ~Fe2O2.25 shows lower surface oxygen potential, which is beneficial to the formation of H2 and N2. Results suggest that reasonable control of the oxidation state of iron oxide can optimize the NH3 CLC process for H2 production.

Redox Photochemistry on Van Der Waals Surfaces for Reversible Doping in 2D Materials

AbstractDespite the van der Waals (vdW) surfaces are usually chemically inert, un‐destructive, scalable, and reversible redox reactions are introduced on the vdW surfaces of 2D anisotropic semiconductors ReX2 (X = S or Se) facilitated by simple photochemistry. Ultraviolet (UV) light (with humid) and laser exposure can reversibly oxidize and reduce rhenium disulfide (ReS2) and rhenium diselenide (ReSe2), respectively, yielding a pronounced doping effect with good control. Evidenced by Raman spectroscopy, dynamic force microscopy, transmission electron microscopy, and X‐ray photoelectron spectroscopy, the grafting and removal of covalently functionalized oxygen groups on the perfect vdW surfaces are confirmed. The optical and electrical properties can be thereby reversibly tunable in wide ranges. Such optical direct‐writing and rewritable capability via solvent/contaminant‐free approach for chemical doping are compelling in the coming era of 2D materials.

Protected long-time storage of a topological insulator

The physical investigation of surfaces and their properties crucially depends on their quality. Such investigations are commonly performed in an ultra-high vacuum environment. Thereby, the transfer of samples among different setups and under ambient conditions is desirable. The usage of a capping layer for the protection of surfaces against contaminations during long-time storage and transfer, and the subsequent temperature-controlled decapping is an established approach. However, a residual-free removal of the capping layer may present a challenge. Here, we systematically investigate the decapping process of a tellurium protected topological insulator Bi2Te3. We give evidence for the material segregation from the contaminated capping layer surface to the substrates. Therefore, a simple, temperature controlled decapping is not sufficient. We demonstrate that near perfect surfaces can be reliably obtained even after long-time storage through a combination of an initial argon ion sputtering process and a following heating for decapping. This approach is suitable for dedicated analysis systems as well as for industrial applications, large throughput of samples of arbitrary shapes, and is easily implemented in existing setups.

Copper-indium hybrid derived from indium-based metal-organic frameworks grown on oxidized copper foils promotes the efficient electroreduction of CO2 to CO

This work reports a novel and effective method for the preparation of the copper-indium bimetallic electrocatalysts by the in situ growth of indium-based metal organic frameworks on oxidized copper foils as the precursor. Compared with the oxide-derived copper and the copper-based carbon material derivative grown in situ on oxidized copper foils, the as-prepared copper-indium electrocatalyst with a self-supporting structure, high roughness factor and rich lattice defects exhibits a superior CO Faradaic efficiency of 95% and good stability for the 36-h potentiostatic test at −0.6 V versus a reversible hydrogen electrode. Density functional theory calculations indicated that the indium atoms occupying the surface copper vacancy defects show lower free energy needed for the formation of *COOH and more difficult desorption of *H than indium atoms, supported on the perfect copper surface. Thereby, the copper-indium catalyst promotes CO2 electroreduction to CO and strongly inhibits hydrogen evolution.

Layered Semiconducting 2D Materials for Future Transistor Applications

Down‐scaling of transistor size in the lateral dimensions must be accompanied by a corresponding reduction in the channel thickness to ensure sufficient gate control to turn off the transistor. However, the carrier mobility of 3D bulk semiconductors degrades rapidly as the body thickness thins down due to more pronounced surface scattering. Two‐dimensional‐layered materials with perfect surface structures present a unique opportunity as they naturally have atomically thin and smooth layers while maintaining high carrier mobility. To benefit from continuous scaling, the performance of the scaled 2D transistors needs to outperform Si technology nowadays. There are already quite a few reviews discussing on the material property of potential 2D materials. It is believed that rigorous analysis based on industrial perspectives is needed. Herein, an analysis on channel material selection is presented and arguments on the four selected 2D semiconductors are provided, which can possibly meet the needs of future transistors, including WS2, SnSe, PtSe2, and InSe. The challenges and recent related research progresses for each material are also discussed.

Implant-free iliac crest bone graft procedure shows anatomic remodelling without redislocation in recurrent anterior shoulder instability after short-term follow-up.

With the help of a J-shaped bicortical iliac crest bone graft, the morphology of the glenoid can be augmented without having to use screws to achieve glenohumeral stability. The aim of this retrospective clinical study was to evaluate the clinical stability and function of the shoulder joint as well as the radiological remodelling process and arthropathic outcomes following the J-bone graft technique. 34 patients with recurrent shoulder dislocations and bony glenoid defects were treated with the J-bone graft technique between 2010 and 2018 at our level-I trauma centre. 15 patients (18 shoulders) could be recruited for the study. Pain levels, ASES, UCLA, SST, DASH, Rowe and WOSI Scores were collected using questionnaires. In 13 patients (16 shoulders) the Constant Score, ROM, CT with 3D reconstruction of the glenoid to assess the graft remodelling and X-rays were performed additionally. None of the patients suffered subluxations or recurrent dislocations during the follow-up period. The overall complication rate was 11%. The evaluation using objective and subjective shoulder function scores yielded good-to-excellent results. Radiological assessment at follow-up showed a low rate of moderate-to-severe arthritis (12%) and a high rate of shoulders without any signs of arthritic degeneration (53%). The CT scans all revealed an almost complete restoration of the glenoid with none of the grafts being resorbed. A rise in the average glenoid circumference and glenoid area could be demonstrated between preoperative measurements (81.6 and 82.4%, respectively) and follow-up measurements (104 and 102.5%, respectively). The results of this study show a successful stabilisation of the shoulder joint and a low complication rate following the J-bone graft technique. Remodelling of the bone graft could be demonstrated, which in turn led to an almost perfect glenoid surface area of 100%.

Hydrophilic graphene oxide-dopamine-cationic cellulose composites and their applications in N-Glycopeptides enrichment

Glycosylation is one of the most important post-translational modifications of proteins, and plays an important role in the structure and function of proteins. However, due to the diversity of glycopeptide forms and their low abundance, it is extraordinarily challenging to capture and separate glycopeptides with high selectivity from complex biological samples with mass spectrometric analysis. Here, we synthesized a new type of hydrophilic composite based on electrostatic interactions, which has been proven to be effective in immobilizing cationic cellulose on graphene oxide-dopamine carriers (expressed as GO-DA-JR), for highly specific enrichment of N-glycopeptides. The introduction of cationic cellulose provides not only a perfect surface charge for the composite but also a greater ability to enrich glycosylated peptides. Thirty-two glycopeptides from human serum immunoglobulin G (IgG) tryptic digests were observed with a greatly improved signal-to-noise ratio (S/N) and also presented high performance in anti-interfering enrichment of glycopeptides from complex samples containing 100-fold bovine serum albumin tryptic digests. In addition, GO–DA-JR has higher sensitivity (1 fmol/μL IgG) and better enrichment capacity (up to 150 mg/g). Moreover, the results of glycopeptide enrichment and glycosylation analysis from human serum also show egood enrichment selectivity from real biological samples. This work exhibits high selectivity, high sensitivity, good stability and operability, indicating its potential for applications of glycopeptides enrichment in post-translational modification proteomics.

Investigation of Coalescence-Induced Droplet Jumping on Mixed-Wettability Superhydrophobic Surfaces

Coalescence-induced droplet jumping has received more attention recently, because of its potential applications in condensation heat transfer enhancement, anti-icing and self-cleaning, etc. In this paper, the molecular dynamics simulation method is applied to study the coalescence-induced jumping of two nanodroplets with equal size on the surfaces of periodic strip-like wettability patterns. The results show that the strip width, contact angle and relative position of the center of two droplets are all related to the jumping velocity, and the jumping velocity on the mixed-wettability superhydrophobic surfaces can exceed the one on the perfect surface with a 180° contact angle on appropriately designed surfaces. Moreover, the larger both the strip width and the difference of wettability are, the higher the jumping velocity is, and when the width of the hydrophilic strip is fixed, the jumping velocity becomes larger with the increase of the width of the hydrophobic strip, which is contrary to the trend of fixing the width of the hydrophobic strip and altering the other strip width.

Machining Operations on Messassa Wood

This study aimed to evaluate the effect of machining operations on the surface quality of the messassa wood (Brachystegia spiciformis and Julbernadia globiflora) for use in the furniture industry. The wood cames from Mozambican Miombo Woodland. The following machining operations were performed: planing, shaping, milling, tearing and boring based on technical standard. The wood had a surface quality approval rating above 70% in all tested machining operations. A perfect surface quality was obtained with a feed speed of 6 m.min-1 in planing. Brachystegia spiciformis had easy workability and extremely well performance compared to Julbernadia globiflora. Nevertheless, both wood species have great potential for use in higher value-added products such as furniture and frame production.

Regularized Yield Surfaces for Crystal Plasticity of Metals

The rate-independent Schmid assumption for a metal crystal results in a yield surface that is faceted with sharp corners. Regularized yield surfaces round off the corners and can be convenient in computational implementations. To assess the error by doing so, the coefficients of regularized yield surfaces are calibrated to exactly interpolate certain points on the facets of the perfect Schmid yield surface, while the different stress predictions in the corners are taken as the error estimate. Calibrations are discussed for slip systems commonly activated for bcc and fcc metals. It is found that the quality of calibrations of the ideal rate-independent behavior requires very large yield-surface exponents. However, the rounding of the corners of the yield surface can be regarded as an improved approximation accounting for the instant, thermal strain-rate sensitivity, which is directly related to the yield-surface exponent. Distortion of the crystal yield surface during latent hardening is also discussed, including Bauschinger behavior or pseudo slip systems for twinning, for which the forward and backward of the slip system are distinguished.

Hexagonal Zr3X (X = Al, Ga, In) Metals: High Dynamic Stability, Nodal Loop, and Perfect Nodal Surface States.

In recent years, topological semimetals/metals, including nodal point, nodal line, and nodal surface semimetals/metals, have been studied extensively because of their potential applications in spintronics and quantum computers. In this study, we predict a family of materials, Zr3X (X = Al, Ga, In), hosting the nodal loop and nodal surface states in the absence of spin–orbit coupling. Remarkably, the energy variation of the nodal loop and nodal surface states in Zr3X are very small, and these topological signatures lie very close to the Fermi level. When the effect of spin–orbit coupling is considered, the nodal loop and nodal surface states exhibit small energy gaps (<25 and 35 meV, respectively) that are suitable observables that reflect the spin-orbit coupling response of these topological signatures and can be detected in experiments. Moreover, these compounds are dynamically stable, and they consequently form potential material platforms to study nodal loop and nodal surface semimetals.

Tuning the Radiative Lifetime in InP Colloidal Quantum Dots by Controlling the Surface Stoichiometry.

InP nanocrystals exhibit a low photoluminescence quantum yield. As in the case of CdS, this is commonly attributed to their poor surface quality and difficult passivation, which give rise to trap states and negatively affect emission. Hence, the strategies adopted to improve their quantum yield have focused on the growth of shells, to improve passivation and get rid of the surface states. Here, we employ state-of-the-art atomistic semiempirical pseudopotential modeling to isolate the effect of surface stoichiometry from features due to the presence of surface trap states and show that, even with an atomistically perfect surface and an ideal passivation, InP nanostructures may still exhibit very long radiative lifetimes (on the order of tens of microseconds), broad and weak emission, and large Stokes' shifts. Furthermore, we find that all these quantities can be varied by orders of magnitude, by simply manipulating the surface composition, and, in particular, the number of surface P atoms. As a consequence it should be possible to substantially increase the quantum yield in these nanostructures by controlling their surface stoichiometry.

A detailed analysis on optical parameters of spinel structured Mn3O4 thin films deposited by nebulized spray pyrolysis technique

Abstract In this work, the role of precursor solution concentration on the diverse optical parameters of nebulized spray deposited spinel structured hausmannite manganese oxide (Mn3O4) thin films derived from the optical measurements are reported for the first time. X-ray diffraction study confirmed that the films belong to the tetragonal structure. This was further substantiated by the Raman measurement where we observe a major peak of single degenerate A1g (symmetry) mode corresponding to Mn–O breathing vibration of Mn2+ ions of spinel Mn3O4. The rod shaped morphology with honey comb pad like feature was identified from the surface morphological study. The strong broad photoluminescence emission peak at 484 nm is associated with the localized levels present near the band gap of Mn3O4. The wettability study indicated that the deposited Mn3O4 films are hydrophilic in nature. The highest optical transmittance of 65.9% was observed for the film and the red shift in transmittance threshold with increasing solution concentration indicated the systematic decrease in optical energy band gap (from 2.93 to 2.43 eV) of the films. The small value of extinction coefficient indicated the perfect surface homogeneity of Mn3O4 films. In addition, various optical parameters such as Urbach energy, plasma resonance frequency, high frequency dielectric constant, optical conductivity, dissipation factor, energy loss functions, lattice dielectric constant, first order linear and third order non-linear susceptibility and non-linear index of refraction of Mn3O4 thin films were calculated and reported for the first time due to variation in solution concentration during deposition. The attempts were made to explain and correlate these results with the help of underlying concepts. The present results will provide new physical insights for the design of any optical device using the spinel structured Mn3O4 films prepared by an amenable technique called nebulized spray pyrolysis.

Heterogeneous oxidation mechanism of SO2 on γ-Al2O3 (110) catalyst by H2O2: A first-principle study

Here, we present a simulation research of the heterogeneous oxidation mechanism of SO2 on Al2O3 (mineral oxides) surface by H2O2, density functional theory (DFT) calculations was used to investigate the adsorption mechanism of SO2 and H2O2 on the perfect and Odefect γ-Al2O3 (110) surfaces. The results show that SO2 molecularly adsorbed on the prefect and Odefect surfaces, while H2O2 was adsorbed in the molecule form on the perfect surface. In particular, H2O2 dissociation only occurred on the Odefect γ-Al2O3 (110) surface. The oxygen defects not only enhanced the adsorption intensities of H2O2 and SO2, but also promoted the H2O2 decomposition (H2O2→OH + OH). Analysis of partial density of states, differential charge density and Mulliken population indicated that H2O2 decomposition followed the Haber-Weiss mechanism (formation of surface OH), and SO2 was oxidized by the OH radicals to form HOSO2 molecule when SO2 and H2O2 co-adsorbed on Odefect γ-Al2O3 (110) surface. Moreover, the lower energy barrier of H2O2 decomposition (32.69 kJ/mol) and SO2 oxidation (78.21 kJ/mol) demonstrated that SO2 to be oxidized easily by the H2O2 on the Odefect γ-Al2O3 (110) surfaces. These results can well explain the formation mechanism of OH radicals and the oxidation mechanism of SO2 by H2O2 on the mineral dust at the molecular level, which is of great significance for understanding the role of H2O2 in the heterogeneous oxidation of SO2 on the mineral dust and the formation mechanism of sulfate aerosols in the atmosphere.

Metal-insulator transition in organic ion intercalated VSe2 induced by dimensional crossover

The charge-density wave (CDW) transition has been extensively studied in transition metal dichalcogenides (TMDs), the underlying mechanism and the related metal-insulator transition are not as simple as Peierls instability in one dimension and still under hot debate. Here, through electrochemical intercalation of organic ions, we have observed a dimensional crossover induced metal-insulator transition in an organic ion intercalated TMDs: ${(\mathrm{TBA})}_{0.3}{\mathrm{VSe}}_{2}$. In pristine ${\mathrm{VSe}}_{2}$, previous studies have revealed a three-dimensional CDW transition at ${T}_{\mathrm{CDW}}\ensuremath{\sim}110\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ with a metallic ground state. After intercalation of organic ions, the remarkable anisotropy of resistivity indicates a highly two-dimensional electronic state in ${(\mathrm{TBA})}_{0.3}{\mathrm{VSe}}_{2}$, which is consistent with our density functional theory (DFT) calculation. Interestingly, the dimensional crossover enhances the CDW transition with ${T}_{\mathrm{CDW}}$ of 165 K and leads to an insulating ground state in ${(\mathrm{TBA})}_{0.3}{\mathrm{VSe}}_{2}$. Moreover, a commensurate superstructure with $3a\ifmmode\times\else\texttimes\fi{}3a$ periodicity is also confirmed in this insulating CDW state. Although the DFT calculation suggests that the commensurate superstructure and the enhanced CDW temperature could be ascribed to the improved Fermi surface nesting, whether the metal-insulator transition is driven by a perfect Fermi surface nesting is still elusive at the present stage. The possible role of electronic correlation and electron-phonon coupling has also been discussed. Our work provides a different material platform to study the metal-insulator transition in TMDs.