Smooth Microstructure Research Articles

The Effect of Heat Treatments and Nickel Additive on The Microstructure and Hardness of 7075 Aluminum Alloy

The aluminum alloys of the 7xxx series consist of Al with Zn mainly, Mg and Cu. 7xxx aluminum alloys has high mechanical properties making it distinct from other aluminum alloys. In this paper, we examine the effect of adding Nickel and heat treatments on the microstructure and hardness of the 7075 aluminum alloy. Were we added different percentages of nickel [0.1, 0.5, 1] wt% to 7075 Aluminum alloy, and applied various heat treatments (artificial aging T6 and Retrogression and re-aging RRA) on the 7075 alloys that Containing nickel. By applying RRA treatment, we obtained better results than the results obtained by applying T6 treatment, and we obtained the high values of hardness and a smoother microstructure for the studied alloys by the addition of (0.5 wt%) nickel to alloy 7075.

The Effect of Heat Treatments and Nickel Additive on The Microstructure and Hardness of 7075 Aluminum Alloy

The aluminum alloys of the 7xxx series consist of Al with Zn mainly, Mg and Cu. 7xxx aluminum alloys has high mechanical properties making it distinct from other aluminum alloys. In this paper, we examine the effect of adding Nickel and heat treatments on the microstructure and hardness of the 7075 aluminum alloy. Were we added different percentages of nickel [0.1, 0.5, 1] wt% to 7075 Aluminum alloy, and applied various heat treatments (artificial aging T6 and Retrogression and re-aging RRA) on the 7075 alloys that Containing nickel. By applying RRA treatment, we obtained better results than the results obtained by applying T6 treatment, and we obtained the high values of hardness and a smoother microstructure for the studied alloys by the addition of (0.5 wt%) nickel to alloy 7075.

Topology optimization of 2-D mechanical metamaterials using a parametric level set method combined with a meshfree algorithm

Two-dimensional (2-D) micro-architectured mechanical metamaterials are designed using a topology optimization approach that integrates a parametric level set method (PLSM) with a meshfree method based on compactly supported radial basis functions (CS-RBF). The PLSM is employed as the optimization algorithm to achieve desired microstructures with targeted material properties. The effective elastic properties, including the bulk modulus, shear modulus and Poisson’s ratio, are predicted using a strain energy-based homogenization method and the CS-RBF meshfree algorithm. Two sets of optimizations are implemented: one is for the case of a single solid material, and the other is for the case of two solid materials, each involving an additional void phase. Three numerical examples are provided for each case with the same optimization objectives: maximizing the effective bulk modulus, maximizing the effective shear modulus, and minimizing the effective Poisson’s ratio under given volume fraction constraints. The numerical results reveal that the newly proposed approach can generate smooth topological boundaries and optimal microstructures. In particular, the current method can topologically optimize auxetic metamaterials with a negative Poisson’s ratio. It can also be extended to design other periodic metamaterials, including those with a negative coefficient of thermal expansion or frequency bandgaps.

Effects of Succinylation on the Physicochemical Properties and Structural Characteristics of Edible Rapeseed Protein Isolate Films

AbstractThis study described the manufacture and characterization of different levels of succinic anhydride (0–15%, w/w) on rapeseed protein isolate (RPI) films. Mechanical, barrier, optical, surface, microstructure, and thermal properties were investigated. Results showed that 5% succinylated rapeseed protein isolate (SRPI) film revealed the overall optimal properties. The mechanical and barrier properties of 5% SRPI film were enhanced significantly compared to the RPI film. The water vapor permeability values of RPI and 5% SRPI films were 0.77 and 0.32 g mm/[hour m2 kPa], respectively. Succinylation improved the color of RPI. The contact angle of 5% SRPI film was 108.68° and was the most hydrophobic combination. Moreover, scanning electron microscopy images revealed that 5% SRPI showed a dense, homogenous, and smooth microstructure. Thermogravimetric analysis results verified a low level of succinylation strengthened the thermal resistance of SRPI films. The content of β‐sheet was almost half of all secondary structures after succinylation, which was supported by analyses of Fourier transform infrared spectroscopy. Results demonstrated that succinylation could be employed to improve the properties of rapeseed protein and SRPI films have great potential to be used as edible films.

Plasma corrosion resistance of aluminosilicate glasses containing Ca, Y and B under fluorocarbon plasma with Ar+

In this study, the corrosion resistance of alumino-silicate glass containing Ca, Y and B is assessed against CF4/O2/Ar plasma, with the results compared to those of poly-crystalline and single-crystalline alumina. All of the alumino-silicate glasses containing Ca, Y and B were more resistant than sintered alumina to a plasma-etching gas. Glass samples with boron oxide were less corroded by plasma than those without B2O3, and their surfaces were contaminated by the CFx generated by the plasma reaction.CaO-Y2O3-Al2O3-SiO2 (CYAS) showed a lower etch rate than sapphire and retained a smooth surface microstructure, unlike sintered alumina. The plasma resistance improved with an increase in the calcium oxide content. The improved plasma resistance of CYAS glass is thought to be due to the high sublimation temperature of the calcium fluoride and the strong atomic binding energy of the calcium ions in the glass.

Preparation and characterization of melamine-resin/organosilicon/Na+-montmorillonite composite coatings on the surfaces of micro-arc oxidation of aluminum alloy

The aim of the present work was to evaluate the effect of the melamine-resin and Na+-montmorillonite and during the synthesis and deposition of organosilicon hybrid coating on 6063 micro-arc oxidation of aluminum alloy and to analyze how these synthesis parameters affect composition, corrosion performance, friction performance and adhesion of the coating resultant. The results show that the existence of melamine-resin/organosilicon/Na+-montmorillonite composite coating greatly improved the corrosion resistance of aluminium alloy, and the associativity between coating and substrate. What’s more, the obtained coating has superior corrosion resistance and frictional resistance. The surface of the coating forms a smooth and smooth microstructure, and the hydrophobicity of the composite coating is obviously improved. The corrosion experiment result indicates the high stability and better adhesion of melamine/organosilicon /Na+-montmorillonite composite coating. It could be used in corrosion environment for a long time.

Development of a water-resistant salep glucomannan film via chemical modification

Deacetylation is a chemical modification process (DD, 0-50-100%) that was applied to purified salep glucomannan at different glycerol concentrations (G, 0-5-10%) to decrease its high hydrophilic film behavior and improve its barrier, mechanical and structural characteristics. The solubility and water vapor permeability of films were significantly reduced by deacetylation. The film mechanical parameters were decreased by 50% DD, but 100% DD increased these parameters compared with the unmodified film. The improved interactions between glucomannan chains induced by deacetylation were revealed by FTIR. SEM results indicated that acetyl-free films had a smooth and compact microstructure when treated with glycerol, but 50% DD films showed aggregation at the surface. XRD analysis showed the conformational rearrangement and improvement in the crystallinity of the films due to deacetylation. Deacetylated films possessed higher thermal stability. Overall, deacetylation provides a promising and potential approach to improve salep film performance, which can benefit its applications in the food industry.

Microstructure characterization of W-Ni-Fe heavy alloys with optimized metallographic preparation method

Tungsten heavy alloys (WHA) have been widely adopted in many engineering applications due to their excellent physicochemical properties. Microstructure characterization is a very powerful method ranging from testing materials properties to detecting material failures and defects. However, the microstructure of WHA was not well characterized with the sample prepared by conventional method of etching with strong acids, bases or oxidant after polishing for the coarse surface. To solve the problem, the exact characterization of W-Ni-Fe heavy alloys microstructure was conducted using the sample prepared by optimized polishing method. A series of experiments were conducted to find the suitable polishing conditions including polishing pad, abrasive slurry and slurry pH. The results show that a smooth and clear microstructure sample was obtained by polishing with alkaline colloidal silica and IC polishing pad, which contained few defects compared with that obtained by conventional method of etching after polishing. The microstructure of W-Ni-Fe heavy alloys was analyzed by XRD, EDS tests and EPMA detection. The slipping phenomenon was observed in nanoindentation test using the prepared sample for the first time and the mechanism of satisfactory microstructure sample preparation was illustrated.

Physical properties of nanostructured ZnO thin films deposited by DC magnetron sputtering method with different volume of O2 in carrier gas

High-quality ZnO thin films with polycrystalline hexagonal structure and (101) preferentially oriented were deposited on Si and corning glass substrates by reactive direct current magnetron sputtering. The effects of different oxygen concentration in carrier gas on structural, morphological and optical properties have been investigated. The increase of O2 concentration resulted in the decrease of preferred orientation intensity and peak shifting to lower 2? values. Scanning electron microscopic images showed a porous tapered columnar structure similar to the zone 1 of Thornton?s structure zone model at lower O2 content and a smooth microstructure similar to the zone T structure at highest O2 content. AFM images showed that film morphology and surface roughness were influenced by O2 concentration. UV-Vis-NIR measurements indicated that the UV absorption intensity of samples was increased and shifted to shorter wavelength (blue shift) at higher O2 concentration. Moreover, the optical band gap increased from 3.91 to 4.41 eV as a function of the oxygen concentration.

Corrosion resistance of a self-healing multilayer film based on SiO2 and CeO2 nanoparticles layer-by-layer assembly on Mg alloys

A multilayer coating with dense and smooth microstructure was successfully constructed on Mg alloys via a novel spin-spray layer-by-layer (SSLbL) assembly technique. As the useful building units, SiO2 nanoparticles could be used as a physical barrier to corrosive medium, and CeO2 nanoparticles were chosen to act as a corrosion inhibitor to heal the physical damage. Thus, the obtained coating possessed good corrosion resistance and self-healing performance, which would prolong the service life of Mg alloy implants.

Effect of Precursor Grain Size on the Sinterability and Conductivity of Commercial Yttria-Stabilized Zirconia as Solid Electrolyte

Solid oxide electrolysis cell (SOEC) and solid oxide fuel cell (SOFC) have been receiving significant attention for future energy storage and hydrogen production applications. This research focuses on the electrolyte material which can be used for both SOEC and SOFC particularly on 8 mol% yttria-stabilized zirconia (8YSZ) electrolyte material. YSZ has been used because of its high stability at elevated temperature, excellent mechanical and chemical properties and its excellent oxygen ion conductivity. This study aims to determine the effect of precursor’s grain size and sintering temperature on the properties of YSZ as electrolyte material for SOEC. Solid-state sintering was done to transform the ceramic powders into solid compacts. Pure cubic fluorite structure YSZ was achieved by both micrograined and nanograined YSZ sintered at 1200°C and 1500°C. It was observed that the micrograined YSZ sample sintered at 1500°C achieved the highest relative density at 99.48%. SEM images showed a smooth and compact microstructure for micrograined YSZ while small pores were still present in the micrographs of nanograined YSZ. However, interestingly, the nanograined YSZ has higher total conductivity as compared to the micrograined YSZ.

Improved ferroelectric properties of (100)-oriented PZT thin films deposited on stainless steel substrates with La0.5Sr0.5CoO3 buffer layers

Ferroelectric Pb(Zr0.53Ti0.47)O3 (PZT) thin films were deposited on La0.5Sr0.5CoO3 (LSCO) buffered stainless steel (SS) substrates by the sol–gel processes. The introduction of LSCO buffer layers facilitated the formation of (100)-oriented PZT thin films, and the (100) orientation degree of PZT thin films was obviously improved from 20 to 62%. Such PZT thin films with smooth and dense microstructures exhibited enhanced remnant polarization, reduced dielectric loss and leakage current density of 42 µC/cm2, 2.7% at 1 kHz, and 7.6 × 10− 7 A/cm2 at 300 kV/cm, respectively. Moreover, the fatigue endurance property of PZT thin films was also improved.

Fabrication of seamless roller mould with smooth surface microstructures by rotation lithography and reflow process

In this work, the authors conducted a versatile approach for an innovative fabrication of a seamless micro-stripes array on the roller which is as a mould for roller imprinting lithography. The major steps in the proposed fabrication method include an uniform speed PR-coating process, followed by a digital micromirrors device based maskless lithography projection and an incremental step-and-rotate exposure process. In addition to above-mentioned steps, a following thermal reflow process was performed to transform the micro-stripes into smooth surface microstructures. The study also analysed the mechanism of the reflow process by numerical simulations and experiments. The mechanism includes the gravitational effect and the definition of the four stages of the reflow process. Study results show that the reflow process on the roller is feasible and the proposed method is a promising approach for fabricating three-dimensional smooth surface microstructures on the roller with different requirements.

Synthesis and Performances of Phase Change Microcapsules with a Polymer/Diatomite Hybrid Shell for Thermal Energy Storage.

The mechanical behavior of phase-change microcapsules (microPCMs) is of vital significance for practical applications in thermal energy storage. Hence, a new type of microPCMs based on an n-octadecane (C18) core and a melamine-urea-formaldehyde (MUF)/diatomite hybrid shell was developed through in situ polymerization. Based on SEM micrographs, most microPCMs exhibited a nearly spherical and smooth microstructure, with broadened particle size distributions. It was confirmed by Fourier transform infrared (FTIR) that successful polymerization of diatomite into the microPCMs occurred, and that additional diatomite had no effect on the core coated by the shell. In addition, the results of the differential scanning calorimeter (DSC) and Atomic Force Microscopy (AFM) demonstrated that the mechanical properties of the microPCMs were remarkably improved by the addition of a moderate amount of diatomite, but that the heat enthalpy and encapsulated efficiency (η) decreased slightly. The incorporation of 2 wt % diatomite resulted in the average Young’s modulus of microPCMs, which was 1.64 times greater than those of microPCMs without diatomite. Furthermore, the melting and crystallization enthalpies and the encapsulated efficiency of the microPCMs were as high as 237.6 J/g, 234.4 J/g and 77.90%, respectively. The microPCMs with a polymer/diatomite hybrid shell may become the potential materials in the application of thermal energy storage.

Synthesis and characterization of Halar® polymer coating deposited on titanium substrate by electrophoretic deposition process

Halar®, an ethylene chlorotrifluoroethylene (ECTFE) thermoplastic polymer, can be considered as an ideal protection coating material for medical application, because of its high purity and unique combination of the mechanical and chemical properties. In this study, Halar® polymer powder particles are deposited onto titanium substrate by the means of electrophoretic deposition (EPD). Differential scanning calorimetry was used to measure thermal characteristics of the raw Halar® powders including glass transition temperature (Tg), melting temperature (Tm) and melting enthalpy (∆Hm). A high crystallinity value was determined for the raw polymer powders by differential scanning calorimetry analysis. Additionally, the effect of heat treatment on Tg, Tm and crystallinity of the polymer are evaluated at different heating temperatures. It was found that heat-treatment of the Halar® powder at the temperature of 260 °C (above its melting temperature) results in increasing of Tg, Tm and crystallinity of this thermoplastic polymer. Thus, after deposition thermal treatment temperature was performed at 260 °C for 15 min which may improve the adhesion of the coating to the substrate and its mechanical properties. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to assess the quality and surface morphology of Ti coated with Halar® polymer. The deposited coating showed a high quality, smooth and homogenous microstructure without any cracks or holes. Nanomechanical properties (hardness and elastic modulus) of the deposited polymer coating were also determined using the nanoindentation technique. Moreover, a comparison is drawn between the fatigue behavior of uncoated and polymer coated Ti specimens by a three-point bend test. The results indicated a blunt crack tip and a higher fatigue strength of Halar® polymer coated Ti.

Electrostatic energy storage in antiferroelectric like perovskite

Lead-free ferroelectric Na0.5Bi0.5TiO3 (NBT) and NBT-doped Ln (Ln = Er and Ho) in both bulk and thin films forms were processed via solid-state reaction and solution deposition respectively. SEM investigations showed dense samples with fine-grained and smooth microstructure for thin films. A pure perovskite structure was observed by the X-ray diffraction for all specimens. The frequency dependences of the dielectric constant and loss tangent were investigated at room temperature and revealed a decrease in the dielectric losses with the introduction of the lanthanide element. The energy storage density (Wrec) was calculated using the obtained P–E loops. The stored and delivered energies were found depending on the form and composition of the sample.

Characterization and performance prediction of jet pulse electrodeposited Ni-SiC nanocomposites by means of artificial neural networks

In this study, Ni-SiC nanocomposites were successfully deposited on Q325 steel substrates using jet pulse electrodeposition. Morphologies, microstructures, microhardness values and corrosion properties of Ni-SiC nanocomposites were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Rockwell hardness testing, and electrochemical apparatus. Microhardness and corrosion properties of Ni-SiC nanocomposites were then predicted by BP artificial neural network and compared to experimental values. Results demonstrated that as-prepared Ni-SiC nanocomposites at pulse current density of 4 A/dm2, SiC particle concentration of 5 g/l and jet rate of 5.5 m/s exhibited maximum microhardness reaching up to ~ 884.2 HV. By contrast, Ni-SiC nanocomposite obtained at current density of 4 A/dm2, SiC particle concentration of 5 g/l and jet rate of 5.5 m/s showed smaller racemule-like surface morphology with smooth, fine, and uniform microstructures. Average grain sizes of Ni grains and SiC nanoparticles were estimated to 53.4 nm and 28.7 nm, respectively. Concentrations of Ni and Si in Ni–SiC nanocomposite fabricated at current density of 3 A/dm2, SiC particle concentration of 3 g/l and jet rate of 4 m/s were recorded as 71.4 at% and 11.7 at%, respectively. Corrosion current density of Ni–SiC nanocomposite deposited at current density of 4 A/dm2, SiC particle concentration of 5 g/l and jet rate of 5.5 m/s revealed minimum corrosion current density of 5.1 × 10−5 A/cm2 and maximum impedance value, demonstrating the optimal anticorrosion ability. Maximum MEs of microhardness and corrosion mass loss of Ni–SiC nanocomposite predicted by proposed BP model were estimated to 3.1% and 3.4%, respectively. These findings suggested that BP model could effectively predict microhardness and corrosion mass loss of Ni–SiC nanocomposites.

Morphology control and upconversion luminescence enhancement of Na1-xLixY.78-yLuyF4:Er.02Yb.2 microcrystals by doping ions with different valences

Trivalent lanthanide ion (Ln3+) doped UC materials can emit visible light under near-infrared (NIR) excitation due to anti-stokes shift and have received wide attention. In this paper, we presented a new strategy to synthesize the uniform and smooth microstructures (rodlike and tubular) based on hexagonal phase NaYF4 microcrystals. Moreover, we systematically discussed the method of enhancing the upconversion (UC) luminescence intensity via co-doping the ions with different valences (Li+ and Lu3+) in order to tailor the environment around lanthanide ions. The UC intensities in the two microstructures were significantly improved. The results suggested the great application potential of tubes and rods of β-NaYF4 microcrystals in anti-counterfeiting, laser media, photonic crystals, and waveguides.

Efficient electrochromic performance of anatase TiO2 thin films prepared by nebulized spray deposition method

Anatase TiO2 thin films with high optical modulation, better reversibility, fast switching time, and enhanced coloration efficiency were prepared by nebulized spray pyrolysis technique. X-ray diffraction study confirmed the formation of anatase phase TiO2 in the present work. This inference was substantiated from the Raman active modes of A1g, 2 B1g, and 3 Eg corresponding to O–Ti–O bond in TiO2. The PL emission peak observed at 400 nm is corresponds to the indirect transition (X1b → Γ3) from the conduction band to the valence band. The average reflectance of TiO2 thin films was varied from 31 to 20%. The electrochemical study revealed the excellent performance of TiO2 films with high optical modulation (ΔT = 61%), fast switching kinetics (t b = 1.6 s, t c = 2.4 s), good coloration efficiency (100 cm2 C−1), and better reversibility (86%). The efficient electrochromic behavior of films may be due to the smooth microstructure nature, which provides an easy pathway for the diffusion and charge transfer process of Li+ ions in TiO2 film matrix. The fast transfer of Li+ ion was realized from the electrochemical impedance spectroscopic measurement.

Crumpled graphene ball-based broadband solar absorbers.

Sheet-like graphene tends to stack with each other in thin films, resulting in relatively smooth microstructures with increased reflection as the thickness increases. In contrast, when the sheets are crumpled into a shape like paper balls, reflection is greatly reduced. In this work, crumpled graphene balls are found to be strong light absorbers in the visible and near-infrared regions. Average absorption of thin films made of crumpled graphene balls can reach up to 97.4% in the wavelength region of 350-2500 nm. When crumpled graphene balls are used as the solar absorber for the interfacial evaporation system, an evaporation efficiency of 84.6% was obtained under one sun at ambient pressure. Enhanced solar absorption of crumpled graphene balls, coupled with their aggregation-resistance and universal solution processability, makes them promising candidates for solar heating/distillation applications.