Effect of ZnO contents at the surface of brass-plated steel cord on the adhesion property to rubber compound

An effect of ZnO concentration at the surface of brass-plated steel cord on the adhesion property between a rubber compound and a brass-plated steel cord was investigated. Cord composition was determined by an Auger microscope with Ar ion sputtering. Two different steel cords were prepared; one (cord A) had higher ZnO concentration at the cord surface compared to the other (cord B). Pull-out force of unaged adhesion sample of cord A was lower than that of cord B. But the adhesion durability of the humidity-aged adhesion sample of cord A was better than the latter. Rubber coverage of the pull out cord for the unaged adhesion samples of cord A was poor, indicating insufficient formation of an adhesion layer. Pull-out force of the thermal-aged adhesion samples decreased with increasing aging time and that of cord A was lower than that of cord B. The enhancement of rubber coverage during initial aging period could be explained by an additional formation of copper sulfide at the adhesion interphase and an increase of modulus of rubber compound adjacent to the adhesion layer. With further increases of aging time, adhesion interphase grew excessively and the physical property of rubber compound deteriorated significantly, such that rubber coverage of adhesion samples decreased markedly with increasing aging time.     

Assessment of printability for printed electronics patterns by measuring geometric dimensions and defining assessment parameters

The printability of patterns for printed electronic devices determines the performance, yield rate, and reliability of the devices; therefore, it should be assessed quantitatively. In this paper, parameters for printability assessment of printed patterns for width, pinholes, and edge waviness are suggested. For quantitative printability assessment, printability grades for each parameter are proposed according to the parameter values. As examples of printability assessment, printed line patterns and mesh patterns obtained using roll-to-roll gravure printing are used. Both single-line patterns and mesh patterns show different levels of printability, even in samples obtained using the same printing equipment and conditions. Therefore, for reliable assessment, it is necessary to assess the printability of the patterns by enlarging the sampling area and increasing the number of samples. We can predict the performance of printed electronic devices by assessing the printability of the patterns that constitute them.

     

Grain Boundary Conformed Volumetric Mesh Generation from a Three-Dimensional Voxellated Polycrystalline Microstructure

We present a new comprehensive scheme for generating grain boundary conformed, volumetric mesh elements from a three-dimensional voxellated polycrystalline microstructure. From the voxellated image of a polycrystalline microstructure obtained from the Monte Carlo Potts model in the context of isotropic normal grain growth simulation, its grain boundary network is approximated as a curvature-maintained conformal triangular surface mesh using a set of in-house codes. In order to improve the surface mesh quality and to adjust mesh resolution, various re-meshing techniques in a commercial software are applied to the approximated grain boundary mesh. It is found that the aspect ratio, the minimum angle and the Jacobian value of the re-meshed surface triangular mesh are successfully improved. Using such an enhanced surface mesh, conformal volumetric tetrahedral elements of the polycrystalline microstructure are created using a commercial software, again. The resultant mesh seamlessly retains the short- and long-range curvature of grain boundaries and junctions as well as the realistic morphology of the grains inside the polycrystal. It is noted that the proposed scheme is the first to successfully generate three-dimensional mesh elements for polycrystals with high enough quality to be used for the microstructure-based finite element analysis, while the realistic characteristics of grain boundaries and grains are maintained from the corresponding voxellated microstructure image.     

Some novel aspects of nanocrystalline diamond nucleation and growth by direct current plasma assisted chemical vapor deposition

Some novel aspects of nanocrystalline diamond (NCD) film nucleation and growth by DC-PACVD were investigated, which focused on the effect of methane injection timing at ramp stage (see discussion in the text) and cathode temperature as well. NCD films were deposited for 4 h on a 4 in. Si wafer which was ultrasonically seeded in a methanol slurry of diamond powder with a 5 nm average diameter. The H₂/CH₄/N₂ gas mixture with a composition of 96.7%/3%/0.3% was used as precursor gas. The total gas flow rate and chamber pressure were 150 sccm and 150 Torr, respectively. Discharge voltage and current of 500 V and 45 A were used respectively at a substrate temperature of 800 °C. The nucleation density, microstructure, growth rate and crystallinity of the obtained NCD films were characterized by SEM, XRD, NEXAFS and Raman spectroscopy. The nucleation density was found to be sensitive to methane injection timing in the ramp stage. In addition, the cathode temperature greatly affected the nucleation density, grain size and growth rate.     

Growth of Ω Plates and Its Effect on Mechanical Properties in Al-Cu-Mg-Ag Alloy with High Content of Silver

In this study, the effects of thermal exposure at 200 °C on the mechanical properties and the growth of Ω plates in an Al-Cu-Mg-Ag alloy with high content of silver were investigated. It was shown that the tensile strength of the exposed alloy decreased with the increase of the mean lengths of Ω precipitates and the decrease in the volume fraction of the Ω phase. The decrease in tensile strength of the 165 °C/14-h-aged samples was less significant than that of 165 °C/2-h-aged samples because the lengthening rate of Ω plates was lower and the number density of Ω precipitates was higher in the 165 °C/14 h-aged samples. The thickening rate of Ω plates was very low during exposure at 200 °C because of high content of silver, and the growth behavior was caused mainly by the lengthening of Ω plates within the habit plane. High content of silver inhibited the thickening of Ω plates and promoted the lengthening of Ω precipitates during exposure.     

Effects of Co content on the Cu diffusion barrier property of electroless NiCoP film

The characteristics of electroless NiCoP films were investigated as a function of Co content. Sheet resistance of a multi-stacked film of SiO₂/Ta/Cu/NiP dramatically increased after annealing at 500 °C, but as more Co was co-plated in NiCoP film, the change in sheet resistance of the stacked film of SiO₂/Ta/Cu/NiCoP at 500 °C became smaller. A CoP/Cu film showed no change in resistance value after annealing, which indicates the CoP film is the most effective Cu diffusion barrier. X-ray diffraction analysis showed that an as-plated NiP film of amorphous structure is easily crystallized by thermal annealing over 300 °C, while CoP showed an insignificant change in crystal structure by thermal annealing up to 500 °C. This result reveals that the CoP film is capable of preventing the diffusion of Cu at 500 °C due to the thermal stability of CoP film.     

High tensile ductility of Ti-based amorphous matrix composites modified from conventional Ti–6Al–4V titanium alloy

Three Ti-based amorphous matrix composites containing ductile dendrites were fabricated by adding alloying elements of Ti, Zr, V, Ni, Al and Be into a conventional Ti–6Al–4V alloy, and the deformation mechanisms related to the improvement of tensile ductility were investigated by focusing on how the effective size of ductile dendrites affected the initiation and propagation of deformation bands or shear bands. The composites contained ～73–76 vol.% dendrites ～63–103 μm in size, and had excellent tensile properties with a yield strength of over 1.3 GPa and an elongation of over 7%. In the composite containing very large dendrites, deformation bands were formed at dendrites in the same direction. In the composite containing small dendrites, however, many deformation bands were actively formed inside dendrites in the several directions, and cross each other to form widely deformed areas. This wide and homogeneous deformation in both dendrites and amorphous matrix enhances the tensile ductility, resulting in high strength and elongation occurring simultaneously. In order to theoretically explain the enhanced tensile ductility, a finite-element method (FEM) analysis based on the real microstructures considering dendrite crystal orientations was performed. The FEM simulation results of deformation bands or shear bands were in good agreement with the experimental findings. The reasons for such a good match between the simulation and experimental results are discussed in detail.     

Shape-controlled fabrication of polypyrrole microstructures by replicating organic crystals through electrostatic interactions

Polypyrrole (PPy) microstructures with diverse shapes were synthesized in an aqueous inorganic salt medium including organic crystals and pyrrole (Py). A series of sulfobenzoic acid salt forms with various cations (K⁺, Na⁺, Li⁺, NH₄⁺) in different positions (para, meta, ortho) of the sulfonate group on the benzene ring were used to form organic crystals as sacrificial templates. Using these crystals, we produced five different shapes of PPy microstructures (hexagonal microplates, curled nanofibers, lozenge-shaped microplates, rigid rods, parallelogram microplates), which replicated the shapes of the organic crystal templates through electrostatic interaction between the anionic crystal surfaces and the cationic PPy chains. In contrast, PPy that was polymerized without crystals showed bulky agglomerates of 200-500 nm size. The electrical properties were dictated by the molecular structures of the organic salt molecules used. While the highest conductivity (200.3 Scm⁻¹) was observed in PPy using crystals of para-linked 4-sulfobenzoic acid monopotassium salt, the lowest conductivity (0.8 Scm⁻¹) was observed in PPy prepared in the presence of crystals of ortho-linked 2-sulfobenzoic acid monoammonium salt.