Crack-free Surface Research Articles

Retail display of beef steaks coated with monolayer and bilayer chitosan-gelatin composites

The effects of edible monolayer and bilayer chitosan-gelatin coatings on the weight loss, lipid oxidation, color preservation (display-life), and shelf-life of beef steaks during 10 days of retail display (at 4 °C; 12 h light/day) were evaluated. The edible coatings had a homogeneous crack-free surface, with the bilayer films being two times thicker than the monolayer coatings. During storage, the control samples had higher pH values and more weight loss (P < .05) than the coated ones. The coatings effectively retarded (P < .05) lipid oxidation and microbial growth (psychrotrophic bacteria, molds, and yeast), extending the shelf-life from 6 to 10 days. The coatings also significantly prevented metmyoglobin accumulation on the beef surface, as reflected in the maintenance of the CIE color indices and sensorial redness perception throughout storage. These effects were similar for both the monolayer and bilayer films, suggesting that chitosan-gelatin coatings could improve the shelf-life and display-life of beef during retail storage.

Curvature-controllable and crack-free AlN/sapphire templates fabricated by sputtering and high-temperature annealing

Post-growth high-temperature annealing of sputtered AlN films is a promising approach to realize high-quality AlN templates for deep-ultraviolet light-emitting diode applications. This paper proposes the double-sided sputtering of AlN on double-sided polished sapphire to suppress the wafer bowing caused by high-temperature annealing. Similar to the case of single-sided sputtering, the twist component of the X-ray rocking curve was markedly improved after annealing, yielding rocking curve widths of 256–321 arcsec in (10–12). By varying the backside thickness, the curvature was controlled from −27 km−1 to 29 km−1, while a crack-free surface was maintained on the front side of AlN. The experimentally obtained curvature and in-plane stress agreed well with the calculation based on thermal stress analysis in the multilayer system.

Development of sputtered Nb3Sn films on copper substrates for superconducting radiofrequency applications

Superconducting radiofrequency (SRF) cavities that could provide a higher quality factor as well as a higher operational accelerating gradient at an affordable cost are in high demand for the future generation of particle accelerators. This study aims to demonstrate the potential of Nb3Sn as material of choice for such SRF applications. Due to its brittle nature, the only way to produce an Nb3Sn SFR cavity is to synthesise a thin layer inside a cavity made of niobium or copper. In this work, direct current magnetron sputtering using a stoichiometric target of Nb3Sn was employed to produce films on copper samples. Assessment of the morphology, microstructure and superconducting properties were performed in order to ensure that this approach is suitable for SRF applications. The potential of the method is proven by obtaining films, which exhibit a crack-free surface, dense morphology and critical temperatures (Tc) up to 16 K. The essential properties of the films have also been investigated with respect to the deposition and annealing conditions. The use of krypton as working gas during deposition increases the atomic percent of Sn in the film compared to argon. However, in contrast to argon, higher krypton pressures reduce the atomic percent of Sn. It was also found that long-lasting high-temperature annealing leads to higher superconducting critical temperatures due to an increased crystallographic order. Particular attention was given to the influence of the copper substrate on the film growth as well as the microstructural and superconducting characteristics. We discuss the main constraints introduced by the copper substrate, such as copper interdiffusion during annealing, lattice mismatch and difference in thermal expansion coefficients and methods to overcome them.

Smoothed particle hydrodynamics (SPH) simulation and experimental investigation on the diamond fly-cutting milling of zirconia ceramics

This paper presents a more efficient ultra-precision diamond fly-cutting method to achieve the damage-free surface machining of hard-brittle zirconia ceramics at one time instead of the traditional abrasive-based processes. Firstly, the smoothed particle hydrodynamics (SPH) cutting simulation model of zirconia ceramics is established in LS-DYNA based on JH-2 constitutive model. The radial diamond fly-cutting milling experiments of zirconia ceramics are carried out on the three-axis ultra-precision machine tool, and the correctness of SPH simulation model is verified by the brittle-ductile transition (BDT) depth and chip morphology. Then, the effects of tool geometry and cutting parameters on stress distribution, brittle-ductile transition depth, cutting force characteristics, and chip morphology are investigated by the proposed model. Some conclusions are given as follows: the tool with more negative rake angle are benefit for hydrostatic pressure and getting greater brittle-ductile transition depth; the critical brittle-ductile transition depths of zirconia ceramics under -15 degree and -35 degree tool rake angle are 0.8μm and 1μm, respectively. Finally, by controlling the maximum undeformed chip thickness below 1μm, an application experiment is carried out and a crack-free nanometer-level surface is achieved in the axial diamond fly-cutting milling of zirconia ceramics.

Crack removal behavior in ultra-precision machining of sapphire

Processing ceramics like sapphire is challenging due to the brittle response exhibited during machining which poses a limitation on maximum material removal rate and throughput of the machining process. Due to this limitation, material has to be removed in small increments in order to create the required form and shape. This study investigates the material response during overlapping machining operation and whether existing surface cracks can be removed by taking advantage of the anisotropy of sapphire. Scribing cuts were performed on the A- and R-plane of sapphire at various depths and the results show that cracks can form during overlapping machining even when the depth of cut is below the critical depth of cut. Experiments on the R-plane of sapphire show that existing surface cracks can be removed by machining over the cracks in a different direction with higher critical depth of cut. Based on these results, development of effective machining strategy to produce crack free surface on sapphire is discussed.

Enhanced dielectric tunable performance of Bi1.5Zn1.0Nb1.5O7/BaTi0.85Sn0.15O3 heterolayer thin films

The Bi1.5Zn1.0Nb1.5O7/BaTi0.85Sn0.15O3 heterolayer thin films are deposited on Pt-Si substrates by radio frequency magnetron sputtering and pulsed laser deposition. X-ray diffraction and atomic force microscopy investigations show that the heterolayer thin films with good crystallinity have crack-free and uniform surface morphology. Experimental results suggest that the BZN layer plays a positive role in enhancing the tunable performance of heterolayer thin films. For the heterolayers, the dielectric constant is ~ 312, calculations of tunability and figure of merit display a high value of ~ 51.7% and ~ 104.7 at 424 kV/cm, respectively. The improvement of figure of merit can be attributed to the boundary introduced by the heterolayer structure.

Colloidal synthesis of CuInS2 nanoparticles: Crystal phase design and thin film fabrication for photoelectrochemical solar cells

This study reports the colloidal synthesis of copper indium disulfide (CuInS2) nanoparticles in different crystal phases to be employed as thin film photoanodes in photoelectrochemical water splitting process. First, CuInS2 nanoparticles with chalcopyrite-, zincblende-, wurtzite-as well as polytypic-phases have been synthesized using hot injection method. The effects of solvent, temperature and type of precursors on the phase design have been thoroughly investigated via various spectroscopic techniques such as XRD, SEM, HRTEM, UV-Vis and PL spectroscopy and Zeta particle size analysis. The XRD spectra have been revealed that the all the targeted nanoparticles had good crystallinity and free from undesired binary sulfides. The synthesized nanoparticles have been re-dispersed in N, N-dimethylformamide (DMF) to form nanoink paste and applied on fluorine doped tin oxide coated glass substrate by doctor blade technique. DMF has been found to be an enviable solvent for thin film fabrication since it could lead to the crack free and uniform surface formation. The chalcopyrite thin film has shown the best photoelectrochemical performance with the photocurrent density of ∼15 mA cm−2 and conversion efficiency of 6.7%. Howbeit, thin films photoanodes bearing wurtzite, zincblende and polytypic CuInS2 nanoparticles have been investigated to compare the performance of different crystal phases for photoelectrochemical solar cell applications. Moreover, it should be emphasized that all thin film electrodes have been investigated under 1-sun condition without any surface modification, chemical treatment and etching. Additionally, the thin films except wurtzite structure exhibited good stability along 2 h under dark and illuminated conditions.

Grown of highly porous ZnO-nanoparticles by pulsed laser ablation in liquid technique for sensing applications

Pulsed laser ablation technique in deionized water with low laser fluency has been explored to prepare uniform dispersed porous ZnO nanoparticles for sensing applications. Surface morphology, particle size, porous structure, roughness, elemental distribution, and chemical bonding of the synthesized ZnO are analyzed by TEM, FESEM, AFM, EDX, and FTIR spectroscopy, respectively. Sensing behavior is observed by UV–Vis absorption measurements. TEM and FESEM analysis show that the prepared ZnO-coated film has homogeneous, dispersed, highly porous, and crack-free surface; the average particle size are observed ~ 24.72 ± 2.97 nm. The porous structure is responsible for appropriate sensing behavior. Low roughness value ~ 1.52 nm which is analyzed by AFM is advantageous for sensing behavior. EDX spectrum and elements mapping clearly show the uniform Zn and O distribution. XRD analysis confirms the hexagonal wurtzite structure of ZnO. FTIR reveals the Zn and O chemical bonding successfully. UV-Visible analysis exhibits that the prepared ZnO matrix has good incorporation with multi-dyes solutions at pH values 10–12 with significant changes in color behavior. The highest pKa value ~ 9.77 at a wavelength of 598.28 nm was calculated for multi-dyes immobilized ZnO matrix. So, it can be concluded that prepared ZnO nanostructures are potential candidates for sensing application.

Pulsed laser deposited bioactive RKKP-Mn glass-ceramic coatings on titanium

The study is aimed at the design of materials, i.e. glass-ceramics, containing trace elements with a specific role in the biological process of regenerating osteoporotic bones. Among these, manganese has a key function in bone osteogenesis and in the maintenance of bone mass. In this work, a 2 wt% of manganese containing RKKP glass-ceramic material has been prepared by sol-gel synthesis. Pulsed laser deposition technique has been applied to deposit films on titanium from the prepared glass-ceramic target. The films have been deposited at two different substrate temperatures (room (RT) and 500 °C) and investigated by X-ray diffraction, Raman spectroscopy, and SEM-EDX techniques. Both the films are characterized by a compact, crack-free and rough surface. The films deposited at 500 °C are composed of crystalline wollastonite and hydroxyapatite phases. For the assessment of films bioactivity in vitro, the standard Kokubo protocol for simulated body fluid (SBF) preparation has been followed. The films deposited at RT and 500 °C have been soaked in SBF for 3, 7, 14 and 28 days. For the film deposited at RT, apatite phase is registered after 7 days of soaking, whereas for the film deposited at 500 °C the apatite appeared only after 14 days. Moreover, the film deposited at RT induces a faster crystallization of the apatite layer.

Functional properties improvement of Ag-ZnO thin films using Inconel 600 interlayer produced by electron beam evaporation technique

500 nm thick silver-zinc oxide (Ag-ZnO) films were grown by electron beam evaporation on 316 L stainless steel (SS) substrate and on 150 nm thick Inconel 600 (IN600) interlayer. The films were annealed in air at 500 °C for 1 h. The morphological and structural analyses confirmed smooth, uniform, homogeneous and crack-free surfaces with nanocrystalline grain size for all films. The elemental composition analysis yielded up to 0.6 wt% Ag in Ag-ZnO/IN600 films. The ultraviolet-visible spectroscopy and Raman spectroscopy along with mechanical and electrochemical tests revealed improved optical, scratch resistance and electrochemical properties of Ag-ZnO/IN600 films than Ag-ZnO films. Ag-ZnO/IN600 and Ag-ZnO films exhibited higher antibiofilm activity against Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans pathogens, comparatively with IN600 films and SS substrate. The superior functional properties of Ag-ZnO/IN600 films suggest their potential for practical applications as antimicrobial and robust coatings on SS surface-contacting medical devices with limited exposure.

Photocatalytic Activity of TiO2/AuNRs–SiO2 Nanocomposites Applied to Building Materials

In this work, the self-cleaning and photocatalytic properties of mesoporous TiO2/AuNRs-SiO2 composites (namely UCA–TiO2Au) prepared by a simple and low-cost technique were investigated toward application in building materials. Mesoporous photocatalytic nanocomposites coating the surface of stone and other building materials are a very promising approach to address relevant questions connected with the increasing atmospheric pollution. We tested three types of preformed TiO2/AuNRs nanostructures in order to evaluate the effect of AuNRs on the photocatalytic activity of resulting coatings deposited on the surface of a popular building limestone. The resulting nanocomposites provide crack-free surface coatings on limestone, effective adhesion, improve the stone mechanical properties and impart hydrophobic and self-cleaning properties. Photocatalytic characterization involved the degradation of a target compound (Methylene blue; MB) under direct exposure to simulated solar light using TiO2 P25 Evonik (TiO2 P25) as a reference material. Moreover, these coatings upon irradiation by simulated solar light were successfully employed for the photocatalytic oxidation of carbon soot. The experimental results revealed that UCA–TiO2Au samples are the best performing coating in both MB bleaching and soot degradation.

CR incorporation in mesoporous silica matrix for fiber optic pH sensing

This research work is concerned with the synthesis of cetyl trimethylammonium bromide (CTAB) assisted silica nanomatrix and creosol red (CR) immobilization in silica nanomatrix. The synthesized nanomatrices are systematically characterized by FESEM/EDS analysis, AFM, FTIR, TGA, BET and UV–vis spectroscopy. FESEM analysis suggests the porous structure network of CTAB assisted silica occupied by CR species after immobilization. Silicon and oxygen signals along with CTAB and CR species by EDS spectra confirm a strong interaction with each other. AFM analysis exhibited the crack-free smooth surface with low average surface roughness ∼2.25 nm which decreased down to ∼1.98 nm. The thickness ∼12 nm is calculated after CR immobilization. FTIR spectroscopy confirmed the presence of silica molecules and CR species bonding after immobilization in silica matrix. BET analysis confirmed the mesoporosity of synthesized matrices with surface area of 458 m2/g, after immobilization. TGA and UV–vis analysis show that thermally stable CR immobilized matrix is 82% transparent and has low refractive index ∼1.38. The proposed sensing device has linear sensitivity ∼90 (a.u.)/pH unit with coefficient of determination (R2) ∼0.98 within pH 1–9. Fast response has been observed at 0.2 s in pH 9 with color change behavior and 98% repeatability identify that the coated matrix has potential in opto-chemical sensing device.

Biomimetic antifouling PDMS surface developed via well-defined polymer brushes for cardiovascular applications

Despite the distinct advantages of poly(dimethylsiloxane) (PDMS) for biomedical applications, because of its hydrophobic nature, suffers from non-specific protein adsorption and platelet adhesion and activation when used as a blood-contacting material. To confer hydrophilicity and biomolecules repelling characteristics, well-defined and high-density poly(2-hydroxyethyl methacrylate) (PHEMA) brushes are synthesized via surface-initiated atom transfer radical polymerization (SI-ATRP) on the PDMS substrate. First, PDMS surface is activated using an ultraviolet/ozone (UVO) wet treatment in water media to introduce hydroxy moieties without scarifying the surface property resulting a crack-free SiO2 surface. Then, 3-(2-bromoisobutyramido)propyl(trimethoxy)silane (BrTMOS), the active ATRP initiator, is immobilized on the UVO-treated PDMS surface to prepare a thin layer of hydrophilic PHEMA brush on PDMS substrate exhibiting excellent protein and platelet resistance. PHEMA brushes supply a biomimetic feature by combining antifouling properties due to hydrophilic characteristic with bioactive properties resulted from the presence of a high density hydroxy groups, which are subsequently used for biomolecules conjugation. The results indicate that grafting of PHEMA chains on the PDMS surface enhances the surface wettability which leads to a decrease in non-specific protein adsorption and platelet adhesion compared to the bare PDMS substrate. The adhered platelets on the PHEMA-tethered PDMS substrate maintain their normal round morphology. Furthermore, the conjugated gelatin macromolecules onto the tethered PHEMA chains promote the adherence and growth of human umbilical vein endothelial cells via ligand-receptor interactions.

Transport and surface charge density of univalent ion of polyvinyl chloride-based barium tungstate ion-exchange composite membrane for industrial separation of waste water

In the present study, a polyvinyl chloride-based barium tungstate ion-exchange membrane was synthesized by sol–gel method. The structure of membrane was studied in terms of Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. X-ray diffraction analysis confirms crystalline form of the composite membrane without any other impurity. Scanning electron microscopy and Fourier transform infrared spectroscopy analysis show the uniform arrangement of particles in the membrane with crack-free surface structure and presence of different functional groups of the organic-inorganic materials. The electrochemical properties like surface charge density ( D), transport number and mobility ratio of the ion-exchange composite membrane were theoretically evaluated and compared with observed values using “Teorell, Meyers and Sievers” method. Transport number follows the order as KCl &lt;NaCl &lt; LiCl &lt; NH4Cl, while the surface charge density showed reversed order. The results showed that the low concentration of electrolytes favors the high mobility of univalent cation in the present study. The above result proves the analytical utility of polyvinyl chloride-based barium tungstate ion-exchange membrane in environmental management.

Convergent Covalent Organic Framework Thin Sheets as Flexible Supercapacitor Electrodes.

Flexible supercapacitors in modern electronic equipment require light-weight electrodes, which have a high surface area, precisely integrated redox moieties, and mechanically strong flexible free-standing nature. However, the incorporation of the aforementioned properties into a single electrode remains a great task. Herein, we could overcome these challenges by a facile and scalable synthesis of the convergent covalent organic framework (COF) free-standing flexible thin sheets through solid-state molecular baking strategy. Here, redox-active anthraquinone (Dq) and π-electron-rich anthracene (Da) are judiciously selected as two different linkers in a β-ketoenamine-linked two-dimensional (2D) COF. As a result of precisely integrated anthraquinone moieties, COF thin sheet exhibits redox activity. Meanwhile, π-electron-rich anthracene linker assists to improve the mechanical property of the free-standing thin sheet through the enhancement of noncovalent interaction between crystallites. This binder-free strategy offers the togetherness of crystallinity and flexibility in 2D COF thin sheets. Also, the synthesized porous crystalline convergent COF thin sheets are benefited with crack-free uniform surface and light-weight nature. Further, to demonstrate the practical utility of the material as an electrode in energy-storage systems, we fabricated a solid-state symmetrical flexible COF supercapacitor device using a GRAFOIL peeled carbon tape as the current collector.

Effects of Heat Treatment on Structural, Optical and Magnetic Properties of Electro Deposited Fe–Ni–P Thin Films

Nanocrystalline Fe–Ni–P thin films have been prepared by electrodeposition method for different temperature. The structural, morphological, mechanical and magnetic properties are analyzed by different measurements. The structural and surface morphology of thin film were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). XRD results showed all the electro deposited Fe–Ni–P films exhibits nanocrystalline FCC structure. The SEM pictures of Fe–Ni–P thin films show that the deposits of thin films are crack free, uniform and bright surface. The mechanical properties of Fe–Ni–P thin films have been analyzed by VHT. The electroplated Fe–Ni–P thin films were strongly adherent to the copper substrate. The VHT result of Fe–Ni–P thin films shows that thin film coated at high bath temperature has highest hardness value. Also VSM result shows that thin film coated at high bath temperature has higher magnetization value. This shows that the soft magnetic properties of Fe–Ni–P thin films are greatly enhanced by various temperatures.

A Cumulative Approach to Crystalline Structure Characterization in Atomistic Simulations

Crystalline characterization poses a challenge when atomic deformation and phase transformation are occurring in an atomic simulation. Crystalline solids are typically characterized by parameters used to classify local atomic arrangements in order to extract features such as crack tips, dislocations, and free surfaces. One such characterization parameter, the common neighborhood parameter (CNP), has been used as an approach to characterize those features with an enhanced formulation applicable to non-monoatomic interactions. The present work introduces a novel approach that extends the CNP to characterize crystalline structures by means of cumulative common neighborhood parametrization (CCNP) for arbitrary structures. The method is compared with the centrosymmetry parameter (CSP) and the common neighborhood parameter (CNA). The methods were applied to a molecular dynamics (MD) simulation of uniaxial tension in an aluminum nanowire. The results showed CCNP’s superior performance in detecting distinct surfa...

Enhancement of mechanical properties and corrosion resistance of NiTi alloy by carbon plasma immersion ion implantation

NiTi alloys are used in orthodontic and orthopedic applications but the long-term corrosion resistance and related properties need improvement in order to satisfy the demand by more stringent applications. In this study, carbon plasma immersion ion implantation (C-PIII) is performed to improve the corrosion resistance and mechanical properties of the Ni50.8Ti49.2 (at.%) alloy. The structure, morphology, chemical and mechanical properties, and corrosion resistance are investigated systematically. A uniform, smooth, and crack-free surface layer with a thickness of 50 nm is produced after C-PIII for 2 h. C-PIII also changes the roughness, hardness, and elastic modulus from 17.4 nm, 64.31 GPa, and 2.74 GPa for the pristine NiTi alloy to 6.1 nm, 89.27 GPa, and 4.77 GPa of the C-PIII sample, respectively. Electrochemical impedance spectroscopy (EIS) indicates that C-PIII improves the corrosion resistance and hardness of NiTi. No surface defects are observed and the reinforced surface structure improves the corrosion resistance by 85%. Penetration of corrosive ions during immersion in 3.5% NaCl results in failure of the passive layer but subsequent reactions with titanium re-form the passive layer. The passive layer is more stable at the immersion time point of 96 h and C-PIII also increases the pitting or local corrosion resistance.

Nano-crystalline TiO2 thin film: Synthesis and investigation of its optical switching characteristics

Optical-switching property of nano-crystalline TiO2 thin films of thickness ~ 100 nm synthesized using sol-gel assisted spin coating method on ~ 0.14 mm thick Al substrate were investigated in this work. The structural analysis of TiO2 thin film show its polycrystalline nature with anatase phase. Surface analysis of the film via scanning electron microscopy and atomic force microscopy show rough TiO2 surface with nearly crack free surface. Current-voltage measurement carried out on this sample (Pt/TiO2/Al) in dark and under optical illumination show enhancement in dark current under optical illumination resulting from photo generation of charge carriers in TiO2 thin film. In addition to this, it also gives rise to optical-switching in the current from low to high and high to low as the illumination was ON and OFF. These results suggest that nano-crystalline TiO2 thin film based optical-switching devices have potential for integrating current device technology towards exciting photo-active device technology.

Atomistic insights on the nanoscale single grain scratching mechanism of silicon carbide ceramic based on molecular dynamics simulation

The precision and crack-free surface of brittle silicon carbide (SiC) ceramic was achieved in the nanoscale ductile grinding. However, the nanoscale scratching mechanism and the root causes of SiC ductile response, especially in the atomistic aspects, have not been fully understood yet. In this study, the SiC atomistic scale scratching mechanism was investigated by single diamond grain scratching simulation based on molecular dynamics. The results indicated that the ductile scratching process of SiC could be achieved in the nanoscale depth of cut through the phase transition to an amorphous structure with few hexagonal diamond structure. Furthermore, the silicon atoms in SiC could penetrate into diamond grain which may cause wear of diamond grain. It was further found out that the chip material in the front of grain flowed along the grain side surface to form the groove protrusion as the scratching speed increases. The higher scratching speed promoted more atoms to transfer into the amorphous structure and reduced the hexagonal diamond and dislocation atoms number, which resulted in higher temperature, smaller scratching force, smaller normal stress, and thinner subsurface damage thickness, due to larger speed impaction causing more bonds broken which makes the SiC more ductile.