Microstructure,dielectric and piezoelectric properties of (Pb1−xSrx)Nb1.96Ti0.05O6 ceramics

(Pb_1−xSr_x)Nb_1.96Ti_0.05O₆ with 2 wt% excess PbO (x = 0, 0.02, 0.04, 0.06, 0.08) piezoelectric ceramics with high Curie temperature were fabricated via the conventional solid state reaction method. Effects of Sr²⁺ amount on crystallite structure, microstructure, dielectric and piezoelectric properties were studied. The substitution of Sr²⁺ ions for Pb²⁺ ions is effective to lower sintering temperatures. X-ray diffraction patterns indicate that all ceramics form the single orthorhombic ferroelectric phase. The doping of Sr²⁺ ions facilitates improving densification of the ceramics. Grain size and lattice parameters of the ceramics vary with the change of the Sr²⁺ contents. Both Curie temperature and maximum dielectric constant change with increasing the Sr²⁺ amounts. The dielectric constant data were also studied using the Curie–Weiss law and modified Curie–Weiss law. The ceramic with x = 0.04 possesses excellent piezoelectric and dielectric properties, presenting a high potential to be used in high-temperature applications as piezoelectric transducers.     

Synthesis of Ni nanoparticles and their characterizations

Ni nanoparticles were synthesized by solution reduction process successfully. The influence of parameters on the size of Ni nanoparticles was studied and the referential process parameters were obtained. The morphology and structure of the synthesized Ni nanoparticles were characterized by transmission electron microscopy (TEM), powder X-ray diffraction (XRD), QELS data and infrared spectroscopy (IR). The result shows that Ni nanoparticles are of high purity and the average size of Ni nanoparticles was found to be 13 ± 2 nm.     

CRYSTALLIZATION BEHAVIOR OF PP IN A NEW GENERATION OF COMPOSITE MATERIAL

The microstructure of isotactic polypropylene (iPP) has been investigated during different steps of the processing of commingled PP/unidirectional glass fiber composites. From wide angle x-ray scattering and differential scanning calorimetry analysis, complemented by density measurements, it can be concluded that the crystalline phase in both un-reinforced PP and composite materials is only constituted of the α phase. The morphology of the crystalline phase and the two-dimensional geometric arrangement of fibers within the matrix of commingled composites reinforced by 45, 60, and 75 wt% of fibers have also been investigated using optical microscopy. The composites exhibit heterogeneous morphology whatever the fiber content is. Moreover, large spherulites can be distinguished, but the presence of a transcrystalline phase around the fibers cannot be detected.     

SITE-RESOLVED WIDE-ANGLE X-RAY STUDIES ON STRUCTURAL PP FOAMS INJECTION-MOLDED BY THE LOW-PRESSURE PROCESS

Structural foam specimens, consisting of three co-axial cylinders of different diameter and length, were injection-molded from isotactic polypropylene, mixed with 0.5 wt% azodicarbonamide as blowing agent, by the classical low-pressure process in a mold cavity (temperature 20°C) pre-pressurized with nitrogen, at melt temperatures of 200, 220, and 240°C, applying different sprue systems and injection directions. Cross-sections were cut from the middle of each cylinder in longitudinal orientation and investigated by site-resolved wide-angle x-ray scattering, making use of the so-called “parallel transmission” geometry. The measurements yielded detailed information about the orientation, dimensions, and interplanar spacings of α-PP crystallites, the distribution of β-PP, and the crystallinity in the cross-sections of the moldings and led to the establishment of general relations between the molding conditions and the microstructure of the moldings in dependence on the configuration of the specimens.     

基于异或软集合的不完备信息系统约减

软集合理论是处理不确定问题的一种新兴数学理论.作为软集合重要的应用领域之一,软集合的参数约减的研究大都基于完备信息系统.介绍了异或软集合的改进运算以及异或软集合决策系统,提出了一种基于异或软集合的不完备信息系统约减方法,同时与拓扑方法相比较.结果表明,算法得出的约减软集合是拓扑法求出的约减软集合的一个子集,即该算法在对数据刻画方面较为细致和全面.     

Study of silica templates in the rice husk and the carbon–silica nanocomposites produced from rice husk

Carbon–silica nanocomposites obtained by rice husk carbonization in a fluidized-bed reactor using a deep oxidation copper–chromium catalyst were studied. Dispersion characteristics of the silica phase in these systems were determined by small-angle X-ray scattering (SAXS) using the full contrast technique. SiO₂ was found in the initial rice husk as compact nanoparticles having a wide size distribution. This distribution consists of a narrow fraction with particle sizes from 1 to 7 nm and a wider fraction with particle sizes from 8 to 22 nm. Oxidative heat treatment of rice husk in a fluidized bed in the presence of the catalyst decreased the fraction of small SiO₂ particles and increased the fraction of large ones. It was demonstrated that the particle size of silica in the carbon matrix can be determined selectively for deliberate design of porous carbon materials with desired properties.     

Ferroelectric and dielectric behaviour of Bi0.92La0.08FeO3 multiferroic thin films prepared by soft chemistry route

Bi_0.92La_0.08FeO₃ (BLFO) thin films were grown on platine substrates by the soft chemical route. Ferroelectric and dielectric behaviors of BLFO films deposited by spin-coating technique and annealed at 773 K for 2 h in air atmosphere were explained. BLFO thin films obtained presents a rhombohedral structure. The BLFO films present dielectric and ferroelectric behaviors with dielectric permittivity and dielectric loss of approximately 81 and 0.0144 at 1 kHz. The Au/BLFO/Pt capacitor shows a hysteresis loop with remnant polarization of 20.6 μC/cm² and coercive field of 53.88 kV/cm. The polarization switching and the fatigue behavior of the BLFO films were significantly enhanced.     

Eutectic alloy microstructure: atomic force microscopy analysis

The exciting microstructures found in several eutectic alloys are a result of a cooperative growth, which is connected to the atomic transfer in the melt ahead the solid/liquid interface. In a eutectic system, the growth of solid phases depends on the simultaneous rejection of constituents to the liquid phase, which causes adjustments of the melt composition and hence, mass transport by diffusion normal to the growth direction. Generally, eutectic microstructures are examined by using optical (OM) and scanning electron microscopy (SEM). While OM may not provide the necessary resolution, the eutectic microstructure may present three-dimensional features, as a result of etching, which is not always possible to be observed by SEM. As an alternative, this paper describes the use of atomic force microscopy (AFM) in understanding micro-scale feature of a eutectic microstructure. For such a purpose, directionally solidified samples of a Ni–Al–V lamellar eutectic, a Ni–Al–Mo fibrous eutectic and a Ni–Al–Nb three-phase eutectic were examined. The results obtained provided a new picture of multi-phase microstructures and allows one to understand their new characteristics.     

Fabrication, assembly and tests of a MEMS-based safe, arm and fire device

We propose a safe, arm and fire (SAF) device that could constitute a real breakthrough for safe miniature fuzing device. It integrates all the functions of a conventional mechanical arm and fire system and integrates them within 1 cm³. For the first time, it combines a mechanical arming unit with electrical safety functionalities on the same silicon initiator's chip. It requires only 635 mW for ignition.     

Effect of geometry on impedance of cell suspended media in electrically mediated molecule uptake using a microstructure

A systematic design and miniaturization of conventional clinical and diagnostic tools are emerging in many nanobiotechnology and nanobioscience fields. Recently, the pharmaceutical and biotechnological industries have continuously accelerated novel drug discovery for cellular therapeutics of hard-to-cure diseases. Electroporation is a promising candidate in gene transfection methods for future cellular therapeutics. Here, we report our initial study on the effect of geometry on impedance of cell suspended media in electroporation using a microchannel. A full understanding of the electroporation environment and conditions enabled us to optimize protocols of electroporation for various cell lines efficiently. Furthermore, this study will open up a new vista of future electroporation devices using microstructures.