Applied Mechanics and Materials Vols. 457-458

Abstract: With sub-micron alumina powder as raw material, high alumina ceramics were prepared through isostatic compaction. The volume density and shrinkage ratio were investigated. The influence of sintering temperature and molding pressure were studied on volume density and shrinkage ratio of ceramic. The results indicated that sintering characteristic of alumina ceramics could be improved at the appropriate sintering temperature and molding pressure and its sintering temperature could be decreased by using sub-micron alumina powder as raw material. 95 ceramics were prepared using sub-micron alumina as raw material, when the sintering temperature was 1550°C, molding pressure was 12 t, and ceramic volume density could be achieved 3.71g /cm³.

Abstract: Well-crystallized SrWO₄ mesocrystals with different shapes including flower-like sphere, bundle, peanut, dumbbell, and notched sphere were controllably synthesized via a simple microwave-assisted precipitation method. X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) measurements were used to characterize these mesocrystals. XRD patterns indicate that the SrWO₄ mesocrystals present a scheelite-type tetragonal structure. FESEM and HRTEM micrographs showed different shapes for the SrWO₄ mesocrystals. The molar ratio of [WO₄^2-] to [Sr²⁺] was found to play an important role in the morphological controlling of the resulting SrWO₄ mesocrystals. With the increase of the molar ratio, the shape of the SrWO₄ mesocrystals changed from flower-like sphere assembled with nanorods to notched sphere with intermediate peanut and dumbbell shapes. PL spectra measurements showed that the luminescence properties of the SrWO₄ mesocrystals strongly relied on its shapes.

Abstract: Ni-P ultra-black films were prepared by ultrasonic chemical etching of electroless plated Ni-P films using 8 mol/L nitric acid at 40 °C for 20 s with different ultrasonic power ranging from 0 to 195 W. Scanning electron microscopy (SEM) was used to study topographic characteristics of the films. The results show that ultrasonic oscillation plays an important role during ultrasonic chemical etching of electroless plated Ni-P films. The enhanced pore features with higher porosity through coalescence of adjacent isolated pores have been observed at 0-105 W. The increase in pore size of Ni-P etched films with the ultrasonic power (from 105 to 195 W) has been confirmed by SEM characterization. Generally, the dependences of relative etching rate on ultrasonic power are closely associated with pore size, pore shape and the distribution of etching pores.

Abstract: For the combination of unique structure, dimension, strength, chemical stability, and electronic properties, carbon nanotubes (CNTs) are very important materials. However, CNTs from commercial sources usually contain some impurities, such as amorphous carbon, metallics, which are usually eliminated by some purification processes that includes reflux in acids and strong oxidation. This strong chemical procedure may damage the nanotube properties and it is thus important to control the extent of oxidation during the purification procedure. In this study, we provide a comprehensive study of the structure and physical composition of CNTs during each step of the purification process. Techniques such as scanning electron microscopy and Infrared spectroscopy were used to track the CNTs structure, in terms of length and diameter distribution, and surface chemical modifications during each purification stage.

Abstract: A simple sugar-derived supramolecular gelator of 1,6-dicaprylate sorbitan ester was designed and prepared as new oil solidifier. The gelation tests revealed that the gelator can gel or phase-selectively gel fuel oils, edible oils and some organic solvents. And the SEM images showed the structure of 3D fiber network was formed in the process of gelation. What’s more, the rate of oil removal in water was 85% and the recovery rate of spilled oils reached up to 60.29%.

Abstract: Materials with infrared low emissivity have attracted great attention due to their increasingly important application in both military stealthy and thermal control. Hence, this work describes a facile, green method based on cotton fibers to fabricate hierarchically structured ZnO fibers and nanorod by simply immersion and calcination process. And infrared emissivity value of samples was also investigated. The cotton fiber adsorbed Zn²⁺ could be converted into ZnO nanorod by controlling reaction temperature and solution pH. The XRD pattern revealed the highly crystalline nature of the samples. In order to enhance the surface optical properties, the surfaces of biomorphic ZnO were modified by bovine serum albumin (BSA). The low infrared emissivity values were obtained in BSA modified samples, indicating that the surface properties of materials may play an important role in infrared emissivity control.

Abstract: Polyethylene/montmorillonite (PE/MMT) nanocomposites were prepared by in situ polymerization. The dynamic mechanical properties and phase structure of PE/MMT nanocomposites at different MMT concentrations (from 0.1 to 1.2 wt %) were studied. The storage modulus of PE/MMT nanocomposites is higher than that of the polymer matrix. And the motions of molecular relaxations and conformational transitions both in non-crystalline and crystalline phases are confined by the strong interactions between polymer and MMT. Otherwise, the spherulite size gradually decreases with the increasing content of MMT.

Abstract: In this work, the effect of γ-irradiation on neat polypropylene (PP) and PP with the stabilizers have been studied by means of wide-angle X-ray diffraction (WAXD) and tensile properties. There is a new reflex 300, β-phase, appeared in irradiated neat PP sample, compared with non-irradiated neat PP sample. When T/S ratio are 0.1 wt%/0.1 wt% and 0.1 wt%/0.3 wt% of PP, the reflex 300 of irradiated PP with different radiation doses all increased. However T/S content is 0.1 wt%/0.5 wt% of PP, the reflex 300 is not appeared. Among the samples which contain stabilizers, the stabilization of PP against γ-irradiation increased, compared with neat PP.

Abstract: Using the finite element software LS-DYNA to establish the shell, fuse, fuse base, cover and charge model of a semi-armor-piercing warhead, and simulating penetration for three different alloy shell of the warhead at a velocity 300m / s, target thickness 34mm . Researching on warhead penetration process, at the same time, analyzing the effects of warhead penetration performance, speed and overload at different alloys material. The results showed that: G50 is the best performance penetrating material, slightly better than the 30CrMnSiNi2A materials. TC4 material is the lowest penetration performance compared to the G50 and 30CrMnSiNi2A material.

Abstract: Materials engineers design, produce and evaluate materials and their use. In this work, the notion of the bivariate generalized multiresolution structure (BGMS) of subspace L^2(R^2) is proposed. The characteristics of bivariate affine pseudoframes for subspaces is investigated. The construction of a GMS of Paley-Wiener subspace of L^2(R^2) is studied. The pyramid decom position scheme is obtained based on such a GMS and a sufficient condition for its existence is provided. A constructive method for affine frames of L^2(R^2) based on a BGMS is established.