We investigate wrinkled thin films by small angle light scattering and microscope, demonstrating that wrinkled thin films are gratings. The diversity of diffraction patterns is realized by a simple light path through wrinkles. Fourier transform is introduced to explain the position and pattern of diffraction orders. The analysis could be a fast and quantized characterization for complex wrinkles.
In this study, the annealing AZ61 magnesium alloy (AO) was studied on friction stir process (AF). The AF specimen revealed that the non-uniform microstructure consists of fine and coarse grains in the stir zone. The FSPed specimens have shown improvement on microstructure and the particles are of matrix distributed over friction stir zone by stabilization heat treatment (AH). The specimens acquired a unique texture twins and basal slip system. The AF and AH specimens possess lower yield stress via friction stir processes and the uniform microstructure of the AH specimen increases the tensile ductility at tensile temperature of 100℃. On the other hand, the AH specimen has the amount of second phase particles and possesses great smooth surface on punch-shear test at 100℃.
A Cu-Ni alloy in which the nickel content was included up to approximately 5 mass% was melted in a graphite crucible with a high frequency induction furnace to prepare the Cu-Ni-Csat (saturated carbon) alloy. Solubility of carbon into Cu-Ni alloy increased with the nickel content and with the melting temperature. The relation between the activity coefficient of carbon for Cu-Ni-Csat and the temperature could be expressed by numerical formulas. This work proposed that the interaction parameter, ωNiC, for Cu-Ni-Csat was −16.1. The precipitated particles from the melt were graphite. Vickers hardness of Cu-Ni-Csat system increased with C content. The Cu-Ni-Csat alloy prepared in this study was hardened by precipitation hardening of the graphite particles and solution hardening of Ni.
The kinetics of the solid-state reactive diffusion between pure Cu and Zn was experimentally examined using sandwich Zn/Cu/Zn diffusion couples prepared by a diffusion bonding technique. The diffusion couples were isothermally annealed in the temperature range of 523–623 K for various times up to 49 h. Owing to annealing, an intermetallic layer consisting of the γ and ε phases was formed at the original interface in the diffusion couple, where the thickness is much smaller for the ε phase than for the γ phase. The total thickness of the intermetallic layer increases in proportion to a power function of the annealing time. The exponent of the power function takes values of 0.60–0.62 at 523–623 K. These values of the exponent indicate that volume diffusion predominantly controls the layer growth and interface reaction partially contributes to the rate-controlling process.
Sulfated anatase TiO2 nanocrystals were prepared by hydrothermal method. All samples were characterized by means of powder XRD and FT-IR. It is shown that all the as-prepared samples displayed the features of pure anatase phase. The surface hydration and sulfation of TiO2 became significantly enhanced as decreasing the particle size. The sulfated TiO2 nanocrystals showed photoactivities towards photodegradation of RhB under UV light irradiation, during which the sulfate species anchored on surfaces of anatase nanocrystals were not released into the reaction solutions.
We have evaluated the diffusion coefficient of phosphorus in α-iron transported in the form of a mixed dumbbell using a kinetic Monte Carlo simulation based on first-principles calculations. The evaluated diffusion coefficient has been compared with both that for the migration mode via octahedral interstitial sites and that for the migration mode of the vacancy mechanism estimated previously using a first-principles-based kinetic Monte Carlo simulation. As a result, we have confirmed that the phosphorus diffusion by the two interstitial migration modes is much faster than that of the vacancy migration mode. In addition, by applying the rate-theory model incorporating the evaluated coefficients to the simulation of irradiation-induced grain-boundary phosphorus segregation, it was made clear that modifications are required to the previous model for GB P segregation and for evaluating GB P coverage.
In-situ TiB2 particles reinforced 2014Al alloy matrix composite was prepared using an exothermic reaction process with K2TiF6 and KBF4 salts. The age-hardening behaviors of in-situ TiB2/2014Al composites were studied using Vickers-hardness measurement, DSC and TEM. The results indicated that TiB2 particles had a considerable effect on the aging response of 2014Al alloy matrix in the composite. Due to the introduction of TiB2 particles, the time to achieve peak hardness in the composite is shorter at three aging temperatures compared with that of 2014Al alloy. While the age-hardness efficiency of the composites was lower than that of 2014Al alloy. Formation of G.P. zones was suppressed in composite, which was believed to be due to the introduction of vast particle-matrix interfaces that acted as a sink for vacancies during quenching. Moreover, TiB2 particles caused increase in thermal-diffusion activation energy of θ′ phase during aging, which made the precipitation of θ′ phase more difficult. And the number and size of precipitates in the composite were relatively less and smaller than that of 2014Al alloy.
Vacuum die castings of AZ91D magnesium alloy were produced at different slow shot speeds and the correlation between density and microstructural features in the vacuum die castings were investigated. The density was measured by using Archimedes method. The microstructure was analyzed with optical microscope, scanning electron microscopy and image analysis software. It was found that the partially solidified gate can be early closed-off by large-size particles at low enough slow shot speeds, which causes high levels of porosity in the vacuum die castings and thus low densities of the castings. Archimedes method is not suitable for evaluating the porosity level in the vacuum die castings. Besides the porosity levels, the densities of the vacuum die castings are related to the ESCs contents in the castings and solidification conditions in the shot sleeve at the beginning of die filling.
A new testing technique named advanced expansion due to compression (A-EDC) has been developed with an attempt to study the hoop mechanical behavior of Zircaloy-4 cladding under the pellet-cladding mechanical interaction (PCMI) and the presumed reactivity-initiated accident (RIA). The Zircaloy-4 used in this work showed elongated grains in the tube longitudinal direction, large amounts of residual strain, and crystallographic texture. The finite element method (FEM) analysis illustrates that the A-EDC test shows a uniaxial tension in the hoop direction, which has also been confirmed by experiments. In addition, the hoop stress-strain curve has been derived at room temperature by the A-EDC tests. Moreover, the fractured surface has been observed in this research.
Creep behaviors and microstructures for two Ni-based heat-resistant alloys with different carbon contents were investigated. The chemical compositions of the alloys were Ni-20Cr-15Co-6Mo-1Ti-2Al-2Nb-0.004 and 0.021C (mass%). The 0.004C and 0.021C alloys are referred to as the low- and high-C alloys, respectively. After solid-solution treatment at 1373 K for 1 h and isothermal annealing at 1023 K for 32 h, fine Ni3Al (γ') particles were formed in the grain interior of both alloys. The average diameter and number density of γ' particles were similar in both alloys. M23C6 carbides were formed on grain boundaries after the isothermal annealing. Coverage ratios with the carbides in the high-C alloy were higher than that in the low-C alloys. Creep tests were performed at 1123 K and 130 MPa. The rupture time for the high-C alloy was longer than that for the low-C alloy, though both minimum creep rates were similar. In the high-C alloy, the creep strain was stored uniformly in the grain interior and the formation of a precipitate-free zone during the creep deformation was suppressed. Therefore, intergranular carbides with a high coverage ratio decreased the creep rate in the acceleration region.
Large amount of dust is produced during ironmaking and steelmaking process and it should be recycled or treated for the sake of environmental protection. Particularly, the dust produced in electric arc furnace (EAF) process is quite special because of its abundance in Zn and Pb, which makes it inappropriate for recycling to the conventional steelmaking process. Chlorination and evaporation method is a possible choice to treat the dust, in which Zn and Pb are selectively chlorinated and recovered as gaseous chlorides while the chlorination of Fe can be prevented in its oxidizing atmosphere. In the present study, the feasibility of the selective chlorination and evaporation reaction of Zn and Pb in EAF dust was confirmed in the mixing atmosphere of Cl2 and O2 gas (PO2 = 9.0 × 104 Pa and PCl2 = 1.0 × 104 Pa). Change of oxide phase with reaction time was also analyzed by XRD measurement. The influence of temperature on the chlorination and evaporation reaction rate and removal fractions of Zn and Pb was investigated by gravimetric method and composition analyses at the temperature range from 923 K to 1073 K. The chlorination and evaporation rate increased with increasing temperature from 923 to 1073 K and the removal fractions of Zn and Pb after 60 min at 1023 or 1073 K reached approximately 98% and 99%, respectively. Simultaneously, it was confirmed that small portion of Fe was chlorinated and evaporated from the dust in the present experimental conditions.
In this work, the facile synthesis of Ag/CuInS2 composite nanoparticles (NPs) with a core-shell structure is demonstrated for the first time. In our procedure, the pre-formed Ag NPs were subsequently coated with a CuInS2 shell through the thermal decomposition of the metal thiolate complex. The Ag/CuInS2 composite NPs took Ag core-CuInS2 shell structures (Ag@CuInS2) when an oleic acid-oleylamine mixture was used as the co-surfactant. High-resolution transmission electron microscopy (TEM) indicated the epitaxial growth of the CuInS2 shell on the Ag NPs. In the extinction spectrum of the Ag@CuInS2 NPs, the localized surface plasmon resonance (LSPR) peak of the Ag core broadened and red-shifted to 2.21 eV, confirming that the LSPR can be tuned by the CuInS2 shell. Finite-difference time-domain (FDTD) simulations indicated the enhancement of the electric field in the CuInS2 shell region and the surface of the Ag@CuInS2 NPs. This enhancement effect may improve the efficiency of incident light absorption in CuInS2 quantum dot sensitized solar cells.
Iron oxide (Fe-oxide) has been widely used in the adsorption of heavy metals from aqueous solution. In this study, we improve the heavy metal adsorption capacity of Fe-oxide by synthesizing its binary oxide with aluminum (Al). In addition, we discuss the effect of characteristic changes caused by Al incorporation on the removal of arsenate (As(V)) and selenate (Se(VI)). Binary oxides with six different Fe:Al ratios (10:0, 9:1, 7:3, 5:5, 3:7 and 1:9) are synthesized by the sol-gel method, followed by a sintering process. The SEM-EDS result reveals that Fe and Al are homogeneously distributed in the oxides. It is found that the incorporation of Al into Fe-oxide not only provides a high specific surface area (90～200 m2/g, 10 times larger than pure Fe-oxide) but also inhibits the phase transition from α-FeOOH to α-Fe2O3. The combination of the expanded surface area and the α-FeOOH phase, which has a plentiful supply of hydroxyl groups, plays a crucial role in improving As(V) and Se(VI) adsorption. Among various Fe:Al ratio binary oxides, the highest uptake is achieved with 5:5 Fe:Al oxide sintered at 100℃.
The corrosion inhibition effect of benzotriazole on copper and steel in simulated tap water was investigated by using potentiodynamic polarization, electrochemical impedance spectroscopy and a quantum chemistry analysis. The corrosion inhibition efficiency for copper and steel was accordingly increased with an increasing of the benzotriazole concentrations. However, the electrochemical test showed a significant difference between the inhibition efficiency of copper and steel. From molecular theory and the adsorption isotherm, the difference between the d-orbital structure of copper and steel affects the adsorption stability of benzotriazole on the metal surface. This postulation is well correlated with the results of the quantum chemical analysis.
Core pins and core blocks are frequently used for aluminum alloy die-casting to produce net-shape parts and/or to prevent the parts from shrinkage in thick casting sections. However, for large casting, some other problems such as soldering of core pin due to insufficient cooling, leakage, etc. may also arise. The authors have studied the heat flow from casting to core pin under various casting conditions and developed an efficient cooling system. This paper reports the optimization of thin wall core pin shape from the perspective of heat flow and mechanicals of core pin. The optimum cooling channel diameter of the core pin should be 70 percent of the outer diameter of the core pin. This thin wall core pin in combination with high pressure water cooling would eliminate soldering and would give a longer core pin life than that of conventional solid core pin without internal cooling.
Chemical vapor deposition (CVD) diamond micro-components are attracting considerable interest due to their exceptional properties and potential applications. Micro-gears are an important actuating component in micro-machines or micro-electromechanical systems. In this study, nano-crystalline diamond duplex micro-gears for micro-machine applications have been fabricated by combining hot filament CVD (HFCVD) with inductively coupled plasma etching. Based on scanning electron microscopy, X-ray diffraction, and micro-Raman spectroscopy observations, the nano-crystalline diamond duplex micro-gears produced by HFCVD are found to be faithful replicas of microstructure silicon molds produced by time-multiplexed deep etching. The fabricated duplex micro-gear consists of two gears. A gear with 14 teeth constitutes the top layer and has root and tip diameters of 1.14 mm and 1.52 mm, respectively, while the second 20-tooth gear constitutes the bottom layer and has root and tip diameters of 1.75 mm and 2.20 mm, respectively. The total thickness of the micro-gear is about 20 μm.
Fig. 3 SEM images of duplex micro-gear produced by HFCVD: (a) morphology of duplex micro-gear; (b) enlarged SEM image of duplex micro-gear. (c) high-resolution SEM image of duplex micro-gear. (d) cross-sectional image of single tooth.
Dissimilar joining of AZ31 Mg alloy to various steel sheets with different coatings (galvanized (GI), galva-annealed (GA), cold rolled bare (CR), and aluminized (Aluminized) steel sheets) was performed by gas metal arc brazing. An excellent weld bead appearance was obtained in all cases and the wettability of the AZ31-GI steel joint was better than that of the other brazed joints. Moreover, the AZ31-CR steel brazed joint exhibited the highest tensile-shear strength. The fracture behaviors of the four brazed joints were different and depended mainly on the chemical composition (especially the Zn content) of the coating layer. Owing to the weak bonding between the Mg-Zn eutectic phase and the Fe-Al intermetallic compound, which formed at the interface of the joint, the strength of the Zn-coated steel (GI and GA steel sheet) joints was lower than that of their non-Zn-coated counterparts.
A stable n-type semiconductor material, ZnPcF16, was synthesized and characterized by infrared (IR), UV-vis and fluorescence spectra. ZnPcF16 showed a monomer characteristic in 1, 2-dichlorobenzene (DCB) while exhibited an aggregation property in tetrahydrofuran (THF) and dimethylformamide (DMF). The ZnPcF16/p-6p (ZnPcF16 on p-6p) organic thin film transistors (OTFTs) using ZnPcF16 as an active layer and p-6p as an inducing layer was fabricated by the physical vapor deposition technique. The ZnPcF16 semiconductor film was characterized by XRD and SEM. And the results showed that ZnPcF16 molecules can be oriented after the employment of the p-6p inducing layer. Charge carrier field-effect mobility (µ) and threshold voltage (VT) of the ZnPcF16/p-6p OTFTs were 1.3 × 10−2 cm2/V s and 22 V, respectively.
The jawbone exists in a special mechanical environment where it is subjected to functional pressure including occlusal force. The internal structure and bone strength of the jawbone might change as a result of tooth loss and implant placement. Therefore, the local bone quality must be evaluated to elucidate the load environment applied to peri-implant jawbone. The present study was conducted to clarify the nanostructural anisotropy of peri-implant jawbone of beagles by quantitatively evaluating biological apatite crystallite alignment. A total of 12 beagles were divided into four groups (dentate jawbone, edentulous jawbone 3 months after tooth extraction, edentulous jawbone 3 months after placing superstructure, and edentulous jawbone 12 months after placing superstructure). Each group comprised three samples. The fourth premolar was considered as the region of interest, with five measurement points in cortical bone around the implant. Each site was subjected to microbeam X-ray diffraction analysis to evaluate biological apatite crystallite alignment. The results revealed that biological apatite crystallite alignment had been lost in the samples taken after tooth extraction. Furthermore, in the dentate and post-implantation samples, preferential alignment was seen not only in the buccal alveolar region, but also in the infraorbital canal and nasal cavity floors. The results of this study suggested that changes of load environment resulting from dental implant treatment contribute to the expression of unique structural characteristics in peri-implant jawbone, which might affect regions relatively far from implants.
Fig. 3 Conceptual drawing of the load transfer path: (a) Dentate: (b) 3M and 12M.
When titanium (Ti) alloys are used for bone fixators after bone fracture, Ti alloys form new bone around themselves in human bone. This ability can cause re-fracture when the fixators are retrieved after bone healing. Surface treatments that do not cause bone formation around Ti alloy are necessary. The purpose of this study was to clarify the inhibitory effect of zirconium (Zr) coating on bone bonding of Ti alloy in rat femur. Non-coated and Zr-coated Ti implants were inserted into the medullary canal of the right and left femur (randomized to side). Four weeks later, the femurs with the implants were removed. The shear strength of implant fixation with the bone was measured by a pull-out test. The amount of the residual new bone adhered on the implants after the pull-out test was evaluated. Pull-out shear strength and the amount of bone elements around implant were lower in Zr-coated group than in non-coated group. Our study indicates that Zr coating inhibits bone bonding between Ti implant and bone in vivo. This technique may be useful to prevent re-fracture when Ti implants are removed from human bone after bone healing.
Pure magnesium and its alloys are biocompatible and biodegradable. In cardiovascular surgery, they have been experimentally applied for short-term use as tiny devices. Many studies have been performed on rats and mice using X-ray imaging and CT scanning. However, these small animals have a low radiation resistance and the lethal exposure dosage is small. In orthopedic surgery, fracture fixation using magnesium materials has high potential applicability. Although long-term stable fixation is required, few long-term animal studies have been performed. Therefore, many unclear issues still remain. Accordingly a long-term animal study was performed on Dutch rabbits to investigate the biodegradation of pure magnesium. Specimens implanted into rabbit femurs showed a volume reduction of 40–50% at 52 weeks. Bone resorption was observed in cancellous bone, and new bone formation and direct contact were partially observed. No magnesium hydroxide was observed in the surrounding area.
The aim of this study was to evaluate the electrochemical corrosion mechanism of AZ31 magnesium alloy by monitoring acoustic emission (AE). AE signals were monitored in situ during the potentiodynamic corrosion test. Evolution of AE signal appeared to be divided into four distinct stages (AE stage I, II, III, and IV) according to the corrosion time and mechanism. AE characteristics in each AE stage were correlated with the bubble behavior, reflecting corrosion mechanism. This interpretation was verified with the simultaneous observation of corrosion bubbling by video camera.
Fig. 1 Polarization curve and corresponding cumulative AE counts divided into four stages during the electrochemical corrosion test.