Advanced Materials Research Vols. 79-82

Abstract: PU/hydrogel compounds prepared byγ-ray radiation technique were investigated in this study. We used nanosized clay solution or powder, Polyurethane (PU), thermosensitive N-isopropyl acrylamide (NIPAAm) and acrylic acid (AAc) as starting materials to prepare PU/hydrogel nanocomposite products. The dipping and weighing tests, Material Testing Machine (LLOYD) were utilized to analyze the physical and mechanical properties differentially. In addition, the drug release and wound closure experiments were also finished by Enzyme-link immunosorbent assay (ELISA) reader and five groups of treatment dressings. From the final results, We obtained that the PU/hydrogel composite incorporating FGF-2 as a wound dressing was able to effectively interact with the wound in a suitable moist healing environment. These composites make them more compatible with skin.

Abstract: At present, the methods of preparing ultrafine explosives are as it follows: mechanical mill method, recrystallization refining method, supercritical fluid method, air stream pulverization method, high-speed impinging method, micro-emulsion method, spray-drying method, direct dilution method, ultrasonic method etc. Although there are so many methods, each one has some inevitable disadvantages. In order to enhance the further research of ultra fine explosives, we mainly place emphasis on the application of recrystallization refining method, supercritical fluid method, jet milling method, high speed impinging method, spray-drying method, ultrasonic method etc.

Abstract: We present the preparation, structural, and magnetic properties of a series of Fe-containing borosilicate glasses as a function of the ratio SiO2/Fe2O3 which is ranging from 1.49 to 2.68. The role of nucleators (Cr2O3 and P2O5) was also investigated. X-Ray diffraction has revealed the formation of magnetite as the major or unique crystalline phase. As SEM micrographs have revealed, the addition of P2O5 give rise to a finer structure as compared with Cr2O3. In addition, the same oxide decreases the temperature of structural transition with almost 100 °C. The magnetization data reveal a two step transition at low temperatures: a high temperature transition at Tv = 128 K, which we attribute to the Verwey transition, and a low temperature transition at Ts = 48 K which, most likely, is the result of change in the dynamic of the domain motion.

Abstract: To obtain intermediate temperature alloy solders with melting temperature of 400~600°C, (Ag-Cu28)-25Sn and (Ag-Cu28)-30Sn alloys were prepared by high energy ball milling. Ag-Cu-Sn nanocrystalline alloys have been obtained after milling for 40h. XRD results show that the (Ag-Cu28)-25Sn alloy consists of Ag4Sn and Cu3Sn, and the (Ag-Cu28)-30Sn alloy contains Ag4Sn, Cu3Sn and Cu6Sn5. The small polydispersed particles with size ranging from 1μm to about 25μm are observed from the (Ag-Cu28)-30Sn alloys milled for 40h by SEM. A large amount of small particles comprised of two or three grains are commonly observed by HRTEM, and average grain size is about 17.50nm. DSC results indicate that the melting points of the (Ag-Cu28)-25Sn and (Ag-Cu28)-30Sn alloys milled for 40h are 548.5°C and 539.3°C, respectively.

Abstract: Mn-doped ZnO nanowires were successfully synthesized on silicon substrate by chemical vapor deposition method with Au catalyst. The X-ray diffraction (XRD) pattern indicates that the Mn-doped ZnO nanowires are hexagonal wurtzite structure and no second phase. The X-ray spectroscopy (EDX) and X-ray photoelectron spectrum (XPS) spectra exhibited the Mn ions were induced into the ZnO nanowires. Photoluminescence (PL) spectra were excited by 325 nm Xe lamp laser. Three peaks are observed in Mn-doped ZnO nanowires, two ultraviolet (UV) emissions at 370 nm and 386 nm, a visible emission at 405 nm. The emission at 405 nm is first found in Mn-doped ZnO nanowires that attributed to the electron transition from bottom of the conduction band to zinc vacancy defect energy level. The existence of Mn element changes the optical property of the ZnO nanowires.

Abstract: Three-dimensional (3D) ZnO nanorod networks were synthesized through the direct evaporation of metal zinc with high purity via a chymical evaporation deposition (CVD) method in Ar and O2 at 910 °C without any catalyst. The nanorod networks of as-synthesized ZnO were characterized using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD). The branches within one network show very regular orientation relationships: either perpendicular or parallel to each other. The nanorods follow a growth direction [0001]. Photoluminescence (PL) spectroscopy were measured at room temperature and showed the different PL features of other nanostructures. Two typical emission peaks at -401 nm and at 452-495 nm were observed. Specially, the emission peak at 452-495 nm includes four subordinate peaks.

Abstract: A new kind of low collateral damage ammunition with Carbon fiber composite material casing is put forward. The operational principle of this ammunition and its configuration are introduced. Then the casting velocity of lethal unit and air shock wave pressure is analyzed theoretically and simulated. In order to study the effect of casing material on blast power, two different kinds of explosive charges are detonated. Overpressure curve of these two charges is measured using the pressure sensors. From the measured overpressure curve and theoretical simulation results, the duration of the positive pressure of the air blast pressure wave caused by the prototype model of the low collateral damage ammunition is bigger than the explosive charge with Carbon fiber composite material casing and naked explosive charge. From the high speed photography, the lethal units flight to a halt at a small distance. These results show the explosive charge with Carbon fiber composite material casing and metal powder can reduce destruction outside the radius of an intended target while enhancing its destructive force on the target.

Abstract: Titania powders consisting of well-crystallized nanosize anatase phase were prepared by the hydrothermal synthesis from Ti(OC4H9)4 at T=568K and P=15.5MPa in the presence of C2H5OH and CO(NH2)2. DTA-TG, XRD and TEM were employed to characterize the samples. The results show that the crystallization temperature of the well-crystallized nanosize anatase phase to rutile is about 1123K, the particles distribute from 10nm to 50nm and it’s average diameter is about 30nm.

Abstract: Carbon nanotubes/ iron compound powder was prepared by high energy ball milling after purified and activated the CNTs. Then, the compound powder and paraffin wax based-binders were mixed to prepare feedstock and the rheological behavior was evaluated by SEM, rheometer and infrared spectrum analysis. By changing the CNTs content and powder loading, the viscosity, shear rate sensitive factor and viscos-activation energy were calculated. 0.2wt% of CNTs, the feedstock can disperse in the binders uniformly without the flowability affecting. Meanwhile, adding proper ratio of CNTs can increase the powder loading of MIM feedstock about 10%, which can optimize the following process conditions and the properties of MIM product.

Abstract: A process of laser cladding of NiCrBSi+2%B4C powder on Ti–6Al–4V substrate to form a coating was carried out, a good coating without cracks and pores was obtained in the process. The microstructure and component of the coating were examined using SEM and EPMA. The interface between the coating and the substrate was metallurgical, The microstructure of NiCrBSi+2%B4C cladding layer consisted of the Ni-based matrix, and the uniformly dispersed reinforcement phases of TiB2, TiC, etc. The microhardness of the coating was measured using a Vickers hardness tester. The average microhardness of the composite coating was HV1200 HV1400, and it was three times higher than that of Ti-6Al-4V substrate.