Advanced Materials Research Vols. 26-28

Abstract: The detailed behavior of the free energy of Cluster Variation Method in the vicinity of spinodal ordering transition is examined. The generalized phase diagram proposed in the previous study is modified and spinodal ordering transition is reinterpreted as a limiting case of the ideal glass transition.

Abstract: In this paper we report the preparation of carbon nanotubes (CNTs) by ethanol catalytic combustion (ECC) technique. We employed cobalt salt as catalyst precursors, copper plate as substrate and ethanol as carbon source. In order to have a better understanding of the growth mechanisms, we employed cobalt chloride, cobalt nitrite and cobalt sulfate as catalyst precursor to study the influence of catalysts on CNTs growth respectively. Entangled and nonseparated CNTs were aggregated together when the catalyst precursor was cobalt chloride, while straight and uniform CNTs were obtained when the catalyst precursor was cobalt sulfate. In the case of using cobalt nitrite as catalyst precursor, the CNTs tend to form helical and disordered structure. We have examined the morphology and microstructure of the obtained CNTs and discussed the growth mechanism.

Abstract: In this paper, we report a simple growth of carbon nanofibers by means of the combustion of ethyl alcohol. In our experiment, copper plate was employed as substrate, iron nitrate and iron chloride as catalyst precursor and ethanol as carbon source. The as-grown carbon nanofibers were characterized by employing scanning electron microscopy, transmission electron microscopy, high-resolution field-emission transmission electron microscopy and Reinshaw optical confocal Raman spectroscopy. Our results suggested that it would tend to form relatively uniform nanofibers when the catalyst precursor was iron nitrate, however, to form some helical structure nanofibers when the catalyst precursor was iron chloride. The sample using iron chloride as the catalyst precursor has a higher graphitization degree than that using iron nitrate as the catalyst precursor.

Abstract: The multi-directional grown carbon nanofibers have been synthesized by catalytic combustion technique. Transmission electron microscopy and selected area electron X-ray diffraction were combined to characterize the carbon products and their catalyst, which promoted the formation of carbon nanofibers. The crystal structures of the catalyst were investigated. The present results indicate that the morphologies of the carbon nanofibers have a close relation with the crystal structure of the catalysts.

Abstract: The present basically concerns with the synthesis of foamy structured amorphous Zrbased alloy, Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 (Vit-1), by liquid state processing. In this method, melt was injected in to the evacuated interstitial voids of the NaCl crystals placed in a copper mould. The casting has been subsequently washed with a jet of water to ensure the removal of NaCl entrapped in the casting, thus resulting in a porous structured casting. It shows the possibility of synthesizing amorphous metal foams with large dimensions using salt infiltration technique.

Abstract: The compositional dependency of the glass forming ability (GFA), magnetic and mechanical properties of the Fe52Co20B20Si4Nb4 bulk metallic glass was investigated by means of the partial substitution of Co either by Al, V or Mo elements. A minor concentration of these elements enabled an increase of the GFA and fully amorphous rods of 4 mm diameter were successfully fabricated for the Fe52Co19B20Si4Nb4Al1, Fe52Co17B20Si4Nb4V3 and Fe52Co17B20Si4Nb4Mo3 alloys. While the addition of Al resulted in an increase of the magnetization saturation, V appeared as the most effective element to enhance the plastic deformation under compression.

Abstract: Bulk metallic glass (BMG) exhibits remarkable properties such as high strength, good stiffness and good corrosion resistance. However, the wear resistance of amorphous metals is not excellent as expected their high strength. It is thought that large local shear bands easily change into cracks for debris formation. The effective obstruction of shear band formation might be applied to improve the wear resistance of BMG. In this study, we tried to suppress shear band deformation by fine crystalline phase dispersion formed by semi-conductor laser irradiation. The microstructures of irradiated Zr-based BMG specimens were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The fine dispersions of crystalline phases are observed in the amorphous matrix. The optimum condition for laser irradiation was discussed.

Abstract: This study dealt with the bending-electrostrictive response of segmented polyurethane (SPU) films, which was a promising candidate for a material to be used in polymeric actuators. Electrostriction is the phenomenon that a material is strained due to both Maxwell stress effect and electrostriction effect developed by the applied voltage. When a dielectric material is subject to an electric field, it will experience Maxwell stress caused by the Coulomb force between accumulated charges and electrostriction by the reorientation of polar phase in the material. In order to SPU having large deformation and force, SPU was composed of the soft segment with poly(tetramethylene glycol), the hard segment with 4, 4’-diphenylmethane diisocyanate, and 1, 4-butanediol. Dielectric actuator based on SPU had good mechanical properties, field-induced strain, and force.

Abstract: Biodegradable polymer multi-layer drug delivery microstructure with micro-chambers has some unique advantages in controlled long-term drug delivery, which can enclose drug in the chambers to realize drug release in a controlled fashion. Therefore, it is necessary to obtain the optimal designs of the micro-chambers and their distributions. In this paper, topology optimization of a three-dimensional biodegradable polymer multi-layer drug delivery microstructure was carried out using the cellular automaton (CA)-based evolutionary structural optimization method. The results show that the optimized controlled release system exhibits a preferable linear drug release profile.

Abstract: Bone microstructure and its functions are maintained by the activity of bone cells such as osteoclast for bone resorption and osteoblast for bone formation. In this study, we examined the role of osteoclast on the formation of the preferential orientation of biological apatite (BAp) as a bone quality parameter using OPG-KO and op/op mouse models in which the expression of osteoclast increases for osteoporosis and decreases for osteopetrosis. The orientation degree of the BAp c-axis was analyzed by a microbeam X-ray diffraction system. We found more decrease in the preferential alignment of the BAp c-axis along the longitudinal direction of bone in the femoral bones of both OPG-KO and op/op mice at 12 weeks compared with normal control mice. We concluded that changes in the amount and activity of osteoclast affect BAp alignment, resulting in the degradation of bone microstructure in osteoporosis and osteopetrosis.