Advanced Materials Research Vols. 47-50

Abstract: In this paper, fatigue crack growth trajectories, crack-front shape and life of the single-side repaired thick aluminium panels with glass/epoxy patch are analyzed. This investigation is performed using three dimensional finite element fracture analyses in general mixed-mode conditions (Mode I, II and III). The obtained fatigue crack growth trajectories, crack-front shapes and lives of the repaired panels with the patch lay-ups of [90]4 and [-45]4 are compared with the available experimental results produced by the authors.

Abstract: The High saturation magnetization (Ms) media are desired to yield large flux density for high resolution giant magnetoresistive head readout in Heat Assisted Magnetic Recording (HAMR). To ensure adequate stability of small size domains, the media for HAMR should possess large coercivity (Hc). In this work, we study of interface wall energy and the behavior of the magnetization of each layer in exchange coupled doubled-layered (ECDL) films. The Tb17Co83 (90 nm)/Tb30Co70 ECDL films with different Tb30Co70 thickness (20, 35, 50, 70, 90 nm) are made to increase the Ms value. As the thickness of Tb30Co70 film increase from 20 to 90 nm, the coercivity of the films increases from 2.5 to 8 kOe. The enhanced coercivity of ECDL films is due to the formation of domain wall at the interface of the ECDL film. As the Tb30Co70 increases from 20 to 90 nm, the Ms value of the films decreases from 380 to 330 emu/cm3. Due to Co has larger magnetic moment than that of Tb at room temperature, the resulting Ms value of the films decreases with increasing the thickness of Tb30Co70 layer.

Abstract: The Tb32Co68/(SiNx/Co)n films (n = 0~3) were prepared by magnetron sputtering. The magnetic anisotropy of all Tb32Co68/(SiNx/Co)n films are perpendicular to the film plane. It is found that the saturation magnetization (Ms) and perpendicular coercivity (Hc⊥ ) of the Tb32Co68/(SiNx/Co)3 film are 263 emu/cm3 and 3592 Oe, respectively. This film appears to be a promising material as a heat-assisted magnetic recording (HAMR) medium. The cross-sectional high resolution transmission electron microscope (HRTEM) images show that the interface roughness between the (SiNx/Co)n layers and TbCo layer increases as n is increased. The rough surface provides more obstacles and pinning sites that hinder the motion of the domain walls at interface between the (SiNx/Co)n layers and TbCo layer. Therefore, the Hc values are profoundly influenced by the interface roughness.

Abstract: This paper presents a complete set of singularity-reduced integral relations for isolated discontinuity embedded in a three-dimensional infinite medium. The development is carried out in a broad context such that the constitutive law governing the material behavior assumes a general form and the discontinuity surface possesses general configuration and jump distribution. The former feature allows the treatment of a well-known class of smart materials (e.g. piezoelectric and piezomagnetic materials) as a special case while the latter renders the treatment of particular types of discontinuity such as cracks and dislocations possible. The key elements utilized in the regularization procedure are special decompositions of two involved kernels in a form well-suited for integration by parts to be performed via Stokes’ theorem. The weakly singular kernels appearing in these representations are obtained in a concise form appropriate for numerical evaluation. A set of integral relations is subsequently specialized to cracks and dislocations. For dislocations, the field quantities such as state variables, the body flux, and the generalized interaction energy are given in terms of line integral representations. The obtained expressions are fundamental and useful in the context of dislocation mechanics and modeling. For cracks, a weakly singular, weak-form integral equation for the surface flux is established. Such integral equation constitutes a basis for a wellknown numerical procedure, a symmetric Galerkin boundary element method (SGBEM). The crucial feature of using the derived integral equation as the key governing equation is its weakly singular nature that allows low order interpolations to be used in the numerical approximation.

Abstract: In this investigation, we propose and experimentally investigate a simply self-restored ring-based fiber Bragg grating (FBG) based sensor system. This proposed multi-ring passive sensing architecture is without any active components in the entire network. In this experiment, the network survivability and capacity for the multi-point sensor systems are also enhanced. Besides, the tunable laser source (TLS) is adopted in central office (CO) for FBG sensing. The survivability of a eight-point FBG sensor is examined and analyzed. Due to the passive sensor network, the cost-effective and intelligent sensing system is entirely centralized by CO. As a result, the experimental results show that the proposed system can assist the reliable FBG sensing network for a large-scale and multi-point architecture.

Abstract: Nanoporous hydroxyapatite ceramic was simply fabricated from nano hydroxyapatite powder and polyvinyl alcohol (as a pore former). The vibro-milling method was used to produce the nano hydroxyapatite composite powder. The powder was then sintered at 1200°C for 3 h. It was found that average porosity of the final product of 64.6±1.4% could be achieved. Open and interconnected pores were obtained with average pore size of less than 100 nm, indicating a nanostructure occurring in the ceramic. In addition, the bending strength of the nanoporous ceramic was measured to be 14.7±3.2 MPa which is practically high for bone repairing applications.

Abstract: The effect of adding small amounts of copper oxide (CuO) on the sintering and mechanical properties of alumina ceramic was studied. Samples were prepared and fired in air atmosphere at temperatures ranging from 1400oC to 1600oC. Sintered samples were characterized to determine phase present, bulk density, hardness and grain size. The results indicated that all the doped samples could be sintered to high density > 3.85 Mgm−3 when compared to the undoped alumina. According to the XRD analysis, the α-Al2O3 phase was not disrupted by the dopant addition. Although the hardness of the CuO-doped material was higher when sintered below 1550°C, the maximum hardness of 21 GPa was measured for the undoped ceramics when sintered at 1600°C. The lower hardness of the doped samples could be attributed to the increased in grain size with increasing sintering temperature.

Abstract: In this study, the chitosan scaffold was modified with the simulated body fluid (SBF) which would create a biomimetic layer on the interface between tissues and scaffolds for the bone formation. To investigate the in vivo osteoinduction, the chitosan scaffolds immersed in the SBF for different times were implanted into the calf muscle in male Wistar rats. The tissues blocks containing the scaffolds were harvested at different periods for bone induction assay and examined histologically. Hematoxyline and Eosin staining (H & E staining), Masson’s Trichriome staining and alkaline phosphatase staining (ALPase), were performed for the observation of in vivo biocompatibility, collagen deposition and ALPase activity. Immunohistochemical staining of osteopontin (OPN) and bone sialoprotein (BSP) were used to examine gene expression of these bone proteins and to determine possible development stage of osteoinduction in the specimens with SBF modification. The results in this research suggested that the SBF modification would improve the biocompatibility of chitosan scaffolds, revealed by the decrease in foreign body reaction. With the SBF treatment, the expression of osteoblastic differentiation, including ALPase, OPN and BSP, would be also enhanced. Besides, the above tendencies would be more significant with the longer time for SBF immersion. In conclusion, the chitosan scaffolds modified by using SBF bioreactor would possess excellent biocompatibility and high potential in the promotion of bone regeneration.

Abstract: The (In15Sb85)100-xBix films (x = 0~18.3) were deposited on nature oxidized Si wafer and glass substrate at room temperature by magnetron co-sputtering of Sb target and InBi composite target. The optical and thermal properties of the films were examined by reflectivity thermal analyzer. Microstructures of the films were analyzed by X-ray diffraction and transmission electron microscope. The crystallization activation energy of the (In15Sb85)100-xBix film (x = 0~18.3) was decreased with increasing Bi content, this indicated that the crystallization speed was improved by doping Bi. The structure of as-deposited (In15Sb85)100-xBix films was amorphous and it would transform to Sb, InSb, Bi, and BiIn2 coexisting phases after annealing at 250 °C for 30 min.