Investigation of the crystallization process and crystal structure of Si-incorporated GeSb phase-change films

The effect of Si incorporation on the crystallization process and crystal structure of Te-free Sb-rich GeSb was investigated in this study. Si concentrations were controlled to 0, 5.1, 9.3, and 12.8 at.% by controlling the sputtering power of the GeSb alloy target (20:80 at.% for Ge:Sb) and Si target. After film deposition, the crystallization process and crystal structure were investigated. Crystallization temperature increased from 320 to 400 °C and the overall crystallinity was decreased with increasing Si concentration. These were analyzed by sheet resistance measurements after thermal annealing and optical contrast measurements by optical static testing. Glass transition temperatures were calculated and increased from 240 to 285 °C with increasing Si concentration. Considering the proportional relation between the glass transition temperature and crystallization temperature, it is thought that more energy is required for crystallization with increased Si concentration. A study of the crystallization process kinetics was conducted by applying the Johnson–Mehl–Avrami model to the optical static test results, which were carried out under a pseudo-isothermal process. The Avrami coefficient was 4.10 and decreased to 3.18 when the crystallization was generated with increased Si concentration from 0 to 12.8 at.%. Therefore, crystallization speed was thought to decrease with increased Si concentration. Based on the results of crystal structure analysis by XRD and HRTEM, the crystal structure of our Sb-rich GeSb PCM was revealed to be a typical Sb structure, i.e., an A7 hexagonal structure with lattice parameters of a = 4.26 Å and c = 11.45 Å. No crystal phase of Ge or Si was observed and no evidence of the structure change in Sb crystals due to Ge or Si incorporation was observed.     

Stress analysis of a stepped rounded D‐ring with a ratio of H1/H2 = 3.0 under uniform squeeze rate and internal pressure by photoelastic experimental hybrid method

Stresses occurring in a stepped rounded D‐ring designed to have a ratio of H₁/H₂ = 3.0 and compressed to 20% squeeze and pressurized with internal pressures of 0 MPa, 0.98 MPa, 1.96 MPa, 3.92 MPa, 4.9 MPa and 5.89 MPa are analyzed using photoelastic experimental hybrid method. It was observed that when a pressure of 0 MPa and 20% compression are applied, the photoelastic isochromatic fringes of the stepped rounded D‐ring with a ratio of H₁/H₂ = 3.0 were almost symmetrical. However, as the applied internal pressure increased, the circular portion of the D‐ring moved over the step on the front side along the points 1_r–2_r towards the restraining wall of the front side of the groove. During the motion of the circular portion, the space between the restraining wall and the step on the front side was slowly filled; but unlike the D‐ring with a ratio of H₁/H₂ = 1.0 where complete filling occurred earlier before extrusion, complete filling of this space delayed until the portion of the D‐ring near the extrusion gap extruded. It was further noted that an internal pressure of up to 5.89 MPa was required to initiate extrusion in the D‐ring with a ratio of H₁/H₂ = 3.0.     

Improving linear processing systems via flexibility

In this paper we tried to improve a given stochastic processing line which is perfectly balanced. By introducing flexibility to a stochastic processing line, we can achieve the benefit of resource pooling. When we apply priority sequencing to the flexible processing line, we can attain an additional reduction in the mean throughput time. By using the heavy traffic approximation the ratio of improvement from flexibility is shown to be significant. We also considered the set-up time loss due to flexibility and derived the appropriate range in which flexibility outperforms set-up time loss. The result of this paper implies that we should consider the alternative of introducing flexibility to a processing system rather than trying to optimally allocate each segments of jobs and get a balanced processing line.     

Silver metallization for microwave device using aerosol deposition

We examined the possibility of using aerosol deposition (AD) as a simple, environmentally friendly and dry metallization process capable of acting as an alternative to the electroless and electroplating methods. Silver thick films were fabricated, their characteristics evaluated, and the factors influencing their growth investigated. As a result, silver thick films were successfully fabricated by AD with high deposition rates (10 μm/min) at room temperature. The resistivity of the as-deposited silver thick films was 8–10 times larger than that of the bulk silver. Post-annealing increased the resistivity of the silver films by approximately 2–3 times compared to that of the bulk silver. Microstructural observations revealed an increase in the connectivity between the silver particles after the heat treatments, which reduced the resistivity of the as-deposited silver films.     

A comparative study on the antioxidative and anti‐allergic activities of fresh and aged black garlic extracts

The antioxidative and anti‐allergic activities of fresh and aged black garlic extracts were investigated. The garlic samples were extracted with 70% ethanol (v/v) and the total phenolic content was measured. The antioxidant capacity of extracts was assessed by determining the scavenging activities on 1,1‐diphenyl‐2‐picrylhydrazyl and hydroxyl radicals, ferricyanide reducing power, ferrous ion‐chelating ability and inhibitory effect on linoleic acid peroxidation. The anti‐allergic activity of extracts was analysed by measuring their inhibitory effects against β‐hexosaminidase release. The aged black garlic exhibited significantly higher phenolic content and greater antioxidative activity than fresh garlic. Both garlic extracts showed strong antioxidant capacity in a dose‐dependent manner. On the other hand, a considerably higher suppression of β‐hexosaminidase release was found in fresh garlic extract at lower concentration compared with that of the black garlic. Results of this study illustrate that ageing of garlic could enhance its antioxidant capacity, but could decrease its anti‐allergic activity.     

Al2O3-nanodiamond composite coatings with high durability and hydrophobicity prepared by aerosol deposition

We attempted the room-temperature fabrication of Al₂O₃-based nanodiamond (ND) composite coating films on glass substrates by an aerosol deposition (AD) process to improve the anti-scratch and anti-smudge properties of the films. Submicron Al₂O₃ powder capable of fabricating transparent hard coating films was used as a base material for the starting powders, and ND treated by 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES) was added to the Al₂O₃ to increase the hydrophobicity and anti-wear properties. The ND powder treated by PFOTES was mixed with the Al₂O₃ powder by ball milling to ratios of 0.01 wt.%, 0.03 wt.%, and 0.05 wt.% ND. The water contact angle (CA) of the Al₂O₃-ND composite coating films was increased as the ND ratio increased, and the maximum water CA among all the films was 110°. In contrast to the water CA, the Al₂O₃-ND composite coating films showed low transmittance values of below 50% at a wavelength of 550 nm due to the strong agglomeration of ND. To prevent the agglomeration of ND, the starting powders were mixed by attrition milling. As a result, Al₂O₃-ND composite coating films were produced that showed high transmittance values of close to 80%, even though the starting powder included 1.0 wt.% ND. In addition, the Al₂O₃-ND composite coating films had a high water CA of 109° and superior anti-wear properties compared to those of glass substrates.     

Triethyl and tributyl phosphite as flame-retarding additives in Li-ion batteries

This study examined the influence of triethyl and tributyl phosphite (TEP and TBP) additives on the electrochemical performance of lithium-ion cells. The cell performance of the TEP- and TBP-containing electrolytes was evaluated by cyclic voltammetry, thermogravimetric analysis, electrochemical impedance spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy. The flammability of the electrolytes was also investigated by measuring the self-extinguishing time of the electrolytes. The results showed that the TEP and TBP additives suppressed the flammability of the electrolyte, with a significant improvement in cell performance observed for the TEP additive. In addition, TEP and TBP additives improved the thermal stability of the battery and its electrochemical cell performance. Overall, 5 wt% TEP and TBP can be used as a flame-retarding additive to improve the cell performance of Li-ion batteries due to the decrease in cell impedance and SEI formation.     

A low‐complexity single‐carrier frequency‐division multiple access transmitter

A framework for a computationally efficient single‐carrier frequency‐division multiple access (SC‐FDMA) transmitter is proposed in this paper. Compared with a wide system bandwidth, the uplink allocation for each user is supposed to be relatively small because of multiple user access, which makes each user's signal vector to be sparse. When the localized subcarrier allocation is used for SC‐FDMA, the inverse fast fourier transform can take advantage of the sparse user input vector to reduce its complexity. The analytical and simulation results show that the proposed framework can provide a significant complexity reduction compared with the conventional SC‐FDMA transmitter. Copyright © 2011 John Wiley & Sons, Ltd.     

A study on the behaviors and stresses of O-ring under uniform squeeze rates and internal pressure by transparent type photoelastic experiment

The behaviors and stresses of an O-ring under uniform squeeze rates and internal pressure change with real time. Therefore, the behaviors and stresses of O-rings under uniform squeeze rates and internal pressures should be studied with real time. To achieve this, a loading device for a transparent type photoelastic experiment, through which various internal pressures and uniform squeeze rates are applied, was developed. The validity of the loading device in analyzing the behaviors and stresses of the O-ring under uniform squeeze rates and internal pressures with real time was verified. It was observed that the filling phenomenon of the O-ring into the space between the lower and front side occurred after forcing out continued for a duration of time. The study also indicated that maximum shear stress would be more effective as a fracture parameter than the maximum normal stress fracture criterion for an O-ring made from rubber.