Advanced Materials Research Vol. 705

Abstract: The dielectric spectrum of CaCu₃Ti₄O₁₂ samples prepared by traditional "one step" ceramic technology is analyzed. It is established that the characteristic Debye-type dispersion with an activation energy 0, 075 eV manifests in the high-frequency range (f ~ 10⁶ Hz). In the low-frequency region (f< 10² Hz) a transition from giant permittivity values to its negative values is detected in some samples. Conditions for such transition are discussed.

Abstract: In this work, CoS flowerlike microclusters with well-aligned nanoflakes were synthesized using a facile solution-phase biomolecule-assisted approach in the presence of L-cysteine (an ordinary and cheap amino acid), which turned out to serve as both the S source and the directing molecule in the formation of cobalt sulfide nanostructures. The morphology, structure, and phase composition of the as-prepared CoS products were characterized using various techniques. The formation mechanism for the cobalt sulfide flowerlike assemblies with well-arranged nanoflakes was also discussed. This facile and solution-phase biomolecule-assisted method can be potentially extended to the preparation of other metal chalcogenides including NiS, PbS, MnS, FeS and CuS nanostructures.

Abstract: Nanoporous copper film (NPCF) electrode was fabricated by applying multicyclic potential scans on a polished copper electrode in an electrolyte composed of ZnCl₂ and benzyl alcohol. Scanning electron microscopy (SEM), Energy-dispersive spectroscopy (EDS), Cyclic voltammetry (CV) and chronoamperometric (CA) were employed to characterize copper chloride modified copper electrode. The Eonset on the copper chloride modified nanoporous copper electrode was 0.5038 V, which was 46 mV lower than that on copper chloride modified copper electrode; Epeak on the copper chloride modified nanoporous copper electrode was 0.9072 V, 814 mV lower than copper chloride modified copper electrode; the jpeak was 15.4 mA cm^-2 higher than that on copper chloride modified copper electrode (9.8 mA cm^-2) in 0.1 NaOH solution in the range of 0 to 1.25 V( vs.Ag/AgCl) at a scan rate of 10mVs^-1.

Abstract: Two series of Fe_81-xNi_xGa₁₉/Si (100) and Fe_81-yNi_yGa₁₉/glass films, where x or y = 0 26at.%Ni, were made by the magnetron sputtering method. We have performed three kinds of experiments on these films: the saturation magnetostriction (λ_S); [ii] the nanoindentation; and [iii] magnetic hysteresis-loop measurements. The main findings of this study are summarized below:[ λ_S reachesa local maximum, when x = 22 and [B] the Youngs modulus, E_f, of the Fe-Ni-Ga film deposited on a Si (100) substrate is larger than that (the same film) deposited on a glass substrate. We conclude thatthe Fe₅₉Ni₂₂Ga₁₉ film could beemployed in a low-field and low-costnano-magnetic switching device.

Abstract: In this paper, the combination method viz. orthogonal signal correction (OSC) and partial least squares (PLS) algorithm is applied to analyze overlapping X-ray fluorescence spectra. The experiment is carried out by using 16 prepared soil samples which are divided into 4 groups according to their different combinations. Prediction results of these 4 groups are respectively calculated using OSC and PLS algorithm. Influence factors of the model are discussed according to specific samples. The experiment result shows that correction factor of OSC can be increased more than one and OSC-PLS algorithm can effectively eliminate the influence of overlapping XRF spectra and improve the predictive accuracy.

Abstract: This research deals with experimentally studied time-dependent deformations of polyvinyl alcohol (PVA) fiber reinforced high performance concrete (HPFRC). The creep in compression and crack propagation of the new concrete compositions were determined. Several kind of concrete mixes adding microsilica and nanosilica have been made. For each composition cylinders with dimensions 190x47mm and Compact Tension (CT) specimens with dimensions 150x150x12mm were prepared. Concrete specimens were tested in a controlled constant temperature and with a constant level of moisture. Creep specimens were put into a creep lever test stand and subjected to a uniform, constant compressive load but CT specimens were subjected to a tension load. Deformations and crack mouth opening displacements were measured with extensometers. The compression strength and modulus of elasticity also were determined. The results have shown that nanosilica dont have significant influence on the high performance fiber reinforced concrete time-dependent behavior.

Abstract: The elastic vibration of semiconducting microcantilever, which was excited with a frequency-modulated pump laser, was optically detected use another probe beam. The photothermal signals were measurement near the resonant frequency. The changes of vibration amplitude and phase with the change of modulation frequency were obtained for a set of different sized microcantilevers. The results showed that the experimental results had a good agreement with the theoretical ones.

Abstract: In this study, the effects of interfacial crack on thermal mechanical behavior of solder bump only induced by current for flip-chip package are investigated by numerical analysis. In the numerical model, the properties of solder bump are dependent on temperature. First, the crack length effects on thermal mechanical behavior of solder bump is examined, with the parameters of temperature, von Mises stress, shear stress and plastic strain. Second, the influence of current density is also numerically examined. It is demonstrated that the increasing current density and the crack length will induce more plastic strain in the solder bump. This study may be helpful for the fabricated technique of the die-solder bump-substrate system.

Abstract: The paper is dedicated to applied problems of dynamic stability of deformable systems. Dynamics of boring columns for shallow drilling (up to 500 m) applied in oil-gas extractive industry is considered. The purpose is investigation of influence of the drill rod's material properties of amplitude-frequency characteristic and stability of movement. Deformation of the drill rod is assumed finite. A model of a compressed-torsioned drill rod is considered within the nonlinear theory of finite deformations of V.V. Novozhilov. Dynamic of elastic movement for steel and dural drill rods applied in the extractive industry, resonant vibration modes and instability zone are investigated. The resonant vibrations of drill rods on the basic and higher (third) frequencies and their stability are calculated.

Abstract: Phase transition of CaB₆ sample under high pressure was studied by in situ electrical conductivity measurements and synchrotron X-ray diffraction up to 26GPa. Three anomalies in conductivity change were found respectively at 3.7, 12.4 and 21.9GPa. X-ray diffraction reveals that CaB₆ transforms from Pm3m to orthogonal structure at 12.32GPa and hence the abnormal conductivity change at 12.4GPa can be attributed to the structural phase transition. The other two anomalies were considered as pressure-induced electronic phase transition in the pressure range of our measurements.