Advanced Materials Design and Mechanics

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Authors: Viorel Sandu, Ivan Ion, Paul Litra-Cristian, Elena Sandu
Abstract: We present the fabrication, structural, and transport properties of MgB2-based ceramic composites with magnetic nanospheres fabricated by spark plasma sintering. The nanospheres are either carbon–encapsulated iron or iron oxide. The former nanospheres have been prepared by laser pyrolysis whereas the iron oxide was obtained by the pyrolysis of the polysiloxane-based copolymers embedded into MgB2 matrix during the sintering process. The structural data show the shrinkage of the a-axis lattice constant as a result of the partial carbon substitution for boron. However, the transport data suggest that carbon diffusion is limited to the outer layer of the MgB2 grains in both cases.
Authors: Jia Zi Shi, Chuan Zhong Chen, Xing Dang
Abstract: Shape memory alloys (SMAs) thin films have attracted much attention in recent years as intelligent and functional materials because of their unique properties. Ferromagnetic shape memory alloys (FSMAs) show large straining output, high impetus and short response time induced by the magnetic field, compared with traditional shape memory alloys. In this paper, Ni-Mn-Ga ferromagnetic shape memory alloys flims prepared by magnetron sputtering are introduced, and the research direction of Ni-Mn-Ga films is presented.
Authors: Kui Huang, Yu Niu, Long Jiang Wang, Yang Liu, Jin San Chen, Ren Zhang Wang
Abstract: The unusual amino acid 3,4-dihydroxyphenylalanine with a catechol side chain is believed to impart both adhesive and cohesive characteristics of mussel adhesive proteins. Inspired by the pH-tunable coordination between catechol moiety and Fe3+, responsible for the high extensibility and self-healing properties of the cuticle of mussel byssal threads, we report the synthesis of a dopamine modified Pluronic F68 block copolymer (PluF68-Dopa) with high coupling efficiency and utilization of catechol-Fe3+ interactions to yield cross-linking hydrogels with enhanced mechanical strength and self-healing properties. Ultraviolet-visible spectroscopy was used to identify PluF68-Dopa-Fe3+ complex species via pH control in dilution solution. At lower pH, concentrated PluF68-Dopa-Fe3+ mixture remained a fluid, whereas at higher pH an elastomeric gel immediately formed. PluF68-Dopa-Fe3+ cross-linked hydrogels are not only pH-responsive but also possess self-healing properties due to the reversible bond interactions between catechol moiety and Fe3+. These new biomimetic materials are expected to have potential biomedical and engineering applications.
Authors: Wen Ding, Vasileios Koutsos, Jin Hai Si, Zhong Xiao Song
Abstract: Active layer’s morphologies properties are important for the optoelectronic devices. In this paper, the morphologies properties of the carbon nanotube/polyaniline composites thin film formed by spin coating were studied by the atomic force microscopy (AFM). The results showed that spin coating way greatly affects the thin film’s topographic image, carbon nanotubes’ concentration is the key that decide whether the interpenetrating network phase separation microstructure can be formed.
Authors: Shi Yan Han, Zhi Ming Liu, Di Wang, Ming Hua Zhu, Yan Li Ma, Yan Yan Zao
Abstract: Three kinds of TiO2 materials named Ti0, Ti0.5 and Ti1.0 were prepared via hydrothermal synthesis method using Tetrabutyl titanate (TNB) as the material and different amounts of Gemini Surfactant we prepared as the template. Then the prepared TiO2 nanoparticle was characterized by Scanning electron microscope(SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Taking the UV light as the light source ,the photocatalytic activity of TiO2 to rhB was studyed . The results showed that the degradation rate of Ti0, Ti0.5 ,Ti1.0 to RhB respectively was 93.6 % , 93.9 %, 99.7 % at the time of 3 hours. The catalytic activity of Ti0.5 and Ti1.0 was obviously better than Ti0, what’s more, Ti1.0 almost made RhB completely degradated at the time of 3 hours.
Authors: Jie Qiu, Shan Dong Li, Mei Mei Liu, Jian Peng Wu, Yi Hu, Xin Le Cai, Jian Hua Lin, Li Li Wang
Abstract: Nanocomposite (Nd,Dy)2Fe14B/α-Fe magnets were prepared by directly solidification (DS). The effect of wheel speed on the magnetic properties, microstructure and exchange coupling interaction has been studied. It was found that a uniform R2Fe14B/α-Fe nanocomposite structure with fine α-Fe grains can be developed at an optimum wheel speed of about 18 m/s. Without any heat treatment, the optimal ribbons (v = 18 m/s) show a strong exchange coupling interaction and good magnetic properties, e.g. iHc=1027 kA/m, mr =0.71, (BH)max=174 kJ/m3.
Authors: Bao Jun Yan, Lei Zhao, Ben Ding Zhao, Jing Wei Chen, Hong Wei Diao, Guang Hong Wang, Wen Jing Wang
Abstract: Hydrogenated amorphous silicon germanium thin films (a-SiGe:H) were prepared via plasma enhanced chemical vapor deposition (PECVD). By adjusting the flow rate of GeH4, a-SiGe:H thin films with narrow bandgap (Eg) were fabricated with high Ge incorporation. It was found that although narrow Eg was obtained, high Ge incorporation resulted in a great reduction of the thin film photosensitivity. This degradation was attributed to the increase of polysilane-(SiH2)n, which indicated a loose and disordered microstructure, in the films by systematically investigating the optical, optoelectronic and microstructure properties of the prepared a-SiGe:H thin films via transmission, photo/dark conductivity, Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR) measurements. Such investigation provided a helpful guide for further preparing narrow Eg a-SiGe:H materials with good optoelectronic properties.
Authors: Min Lu, Xing Zhi Zhao, Xiang An Wang, Yong Bin Ren, Li Wang
Abstract: We report a simple and low-cost method for constructing high-quality p-type ZnSe nanowires/n-type Si heterojunction by growing p-type ZnSe:N nanowires on n-type Si substrate. The heterojunction shows excellent stability and reproducibility to white light irradiation with a fast response time (103). And the photovoltaic characteristics of it exhibit a fill factor of about 24% and a high power conversion efficiency of 0.89%.
Authors: Tao Zhang, Min Li, Ting Liu, Bin Sun, Sheng Nan Zhou
Abstract: The high piezoelectricity and high mechanical quality factor thin films are very important for the fabrications of micro devices. The Pb(Zrx,Ti1-x)O3(PZT) thin films own high piezoelectricity, however, its mechanical quality factor is small. The proper doping of Pb(Mn1/3,Nb2/3)O3(PMnN) will perfectly improve the mechanical quality of the films. However, the doping of PMnN will change the dielectric property of PZT thin films, and so it’s very necessary to investigate the dielectric property of PZT thin films doped with different ratio of PMnN. In this paper, the Pb(Mn1/3,Nb2/3)O3- PbZrO3-PbTiO3(PMnN-PZT) thin films with different doping ratio of PMnN are deposited by the magnetron sputtering method, and the X-ray diffraction is applied to analyze the structure of thin films, and the relative dielectric constant are characterized by the LCR testing system. The results show that the PMnN-PZT thin films with smaller doping ratio than 20% exhibit polycrstal structure, and the dielectric constant of thin films increase with the doping ratio of PMnN sharply, especially the doped PMnN is smaller than 6 mol percent. All the dielectric constants decrease with the testing frequency, and which have little change if the testing frequency is larger than 2.5kHz.

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