Materials Science Forum Vols. 620-622

Abstract: The output quantity of iron tailings increases rapidly with the development of metallurgical industry and the growth of the requirement for minerals in the world, which could cause severe hazard to our environment. Therefore, it is very important to recover and reuse these tailings to protect the environment and use natural resources effectively. In this paper, the Fe-Si-Ti multiphase composite ceramic has been synthesized from the Iron ore tailings of Panzhihua region with the carbothermal reduction nitridation (CRN) method. The phases and microstructures of sintered body were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FSEM) and energy dispersive spectroscopy (EDS). The XRD pattern indicates that the main phases of the samples are Fe3Si and Ti(C0.3, N0.7). Meanwhile, FSEM and EDS show that Fe3Si is surrounded by Ti(C0.3, N0.7). Besides, the physical properties of the sample are tested, especially the wear resistance. The test results show that the synthesized Fe3Si-Ti(C0.3, N0.7) composite ceramic has good wear resistant property, high hardness and larger thermal expansion coefficient, which indicates it can be used as the abrasion-proof material or transition layer between the metal and inorganic coating. At last, based on FSEM and EDS, the microstructure and elements of the abraded surface of sample is analyzed.

Abstract: The barium aluminum silicate-silicon nitride (BAS-Si3N4) matrix-ceramic composite was fabricated using pressureless sintering, at temperatures ranging from 1720°C, which is below the melting point of BAS, to 1850°C. The effect of processing conditions on sinterability, crystalline structure, microstructure and mechanical properties was evaluated. It was demonstrated the BAS glass-ceramic served as an effective liquid-phase-sintering aid, to attain high densities and completed the α-Si3N4–β-Si3N4 phase transformation, and remained as a structural matrix that was reinforced by the rod-like β-Si3N4 grains. Si3N4 grains nucleated and grow in random directions in an almost completely crystallized matrix of hexacelsian BAS. High flexural strength (665±40 MPa) and fracture toughness (7.74 MPa•m1/2) could be obtained from 30wt%BAS-70wt%Si3N4 samples that have been sintered at 1800°C for 120 min with a fine-grained microstructure.

Abstract: Non-contact material removal processes offer numerous advantages over traditional machining approaches and nowhere is this more apparent than in the fabrication of micro devices. Current micromachining techniques such as microgrinding and micromilling have limitations with respect to their positioning accuracy and tool deflections. Electro thermal processes such as microEDM and laser machining usually result in a heat affected zone being produced. Other approaches such as etching and non-contact ultraprecision polishing are either costly or are not suitable for high throughput. In order to address these limitations, alternative micromachining techniques are required. In this paper, a non-contact material removal technique based on the electrokinetic phenomenon is proposed for precise material removal at rates in the order of nanometers/min. The aim of this research is to have a better understanding on the electrokinetic material removal technique by studying the trajectory of the particles and the influence of the frequency of the electric field on the material removal rate.

Abstract: Using TiCl4 and CuCl2 as precursors, the sols were prepared. The coatings of Ti/Cu oxide were formed on both glass and alumina substrates by dip-coating method. XRD results showed that the coatings could be composed of anatase TiO2, CuO and M6O type oxides. The M6O type oxide on glass substrate is in the form of Cu3Ti3O, however is Cu2Ti4O on alumina substrate. The formations of the CuO and M6O are related to the Cu:Ti ratio. A high Cu:Ti ratio corresponds to the CuO, whereas to the M6O. Also the sols were analyzed by infrared spectroscopy and the mechanism of the formation of the coatings was discussed in the paper.

Abstract: Zinc oxide(ZnO) has been widely applied in the fields of cosmetics, paint, coating and gas sensor. Size down of ZnO is essential for the preparation of sol or film of ZnO in the application. The size and shape of ZnO particles are controlled by varying drying method. The ZnO was prepared by mixing of zinc acetate and sodium hydroxide at 0°C. Then it was freeze dried or 20°C vacuum dried. After washing the residual ions, it was further compared by drying at 20°C vacuum drying or 200 °C oven drying. The ZnO powder was characterized by XRD, Brunauer-Emmet-Teller analysis(BET) and transmission electron microscope(TEM). The ZnO have wurzite structure with ~10 nm particle size when it was prepared by freeze drying and then 20°C vacuum drying after washing the residual ions. On the other hand, without freeze drying, the ZnO particles observed to be aggregated to 200~400 nm with primary particle size of ~20 nm. The smaller size of ZnO particle in freezing drying compared to 20°C vacuum drying may be explained by frozen water preventing the growth of ZnO particles.

Abstract: The present paper studied the thermal and mechanical properties of atmospheric pressure plasma jet (APPJ) treated multiwall carbon nanotubes/polypropylene/polylactic acid nanocomposite filaments. The experiments included tensile tests, differential scanning calorimeter (DSC), Scanning electron microscopy (SEM) experiments. DSC studies showed that there were a distinct shift in Tg and a relatively moderate change in Tm for different systems. The activation volumes of CNTs/PP/PLA nanocomposite filaments have been calculated to describe strain rate sensitive behavior of CNTs/PP/PLA nanocomposite filaments by following Eyring’s equation based on the tensile test results.

Abstract: The purpose of the present work is to investigate the microstructural deformation of the montmorillonite (MMT) particles/polypropylene (PP)/polylactic acid (PLA) nanocomposite filaments infused with plasma treated MMT. The activation volumes of the MMT/PP/PLA nanocomposite filaments ranging from 31.4572 to 151.2100 (nm)3 estimated by the Eyring’s equation quantitatively revealed that the plasma treated MMT acted as obstacles to dislocation motion during microstructural plastic deformation mechanisms. DSC analysis showed marked increases in glass transition temperature (Tg), indicating the plasma treated MMT could effectively help resist the free crankshaft movement of the macromolecular chain in the nanocomposite filaments. In addition, the MMT/PP/PLA nanocomposite filaments developed intercalated structures which had been examined by SEM.

Abstract: A green emitting SrAl2O4:Eu2+, Dy3+ phosphor with high brightness and long afterglow was synthesized by the sol-gel method. SrAl2O4: Eu2+, Dy3+ phosphor exhibited broad band extending from 450 to 650 nm and maximum emission spectra peaking at 520 nm. Three excited levels existed, two shoulders were observed at 270 and 330 nm in addition to the maximum at 360 nm on the excitation spectrum. After the removal of excitation light, the excellent after-glow characteristic of the phosphorescence was obtained as a result of low decay time, although the after-glow intensities of phosphor varied exponentially with the time.

Abstract: Length-tailored, monodisperse, highly orientated, single-crystalline hexagonal and aligned ZnO nanowhiskers were grown onto F-doped SnO2 conductive glass (FTO) substrate at 88 °C using an aqueous solution. The aqueous solution for growth of ZnO nanowhiskers included zinc nitrate hexahydrate, hexamethylenetetramine and polyethylenimine. The addition of branched polyethylenimine, which may be adsorbed on the nonpolar surface of ZnO crystals, improved the growth of ZnO nanowhiskers along the c-axis.

Abstract: In the current study the role of plasma treated nano titanium dioxide particles and strain rate on the tensile properties of plasma treated nano TiO2 particles/PP/PLA nano-composites filaments (PTNTOPPCF) was studied. The experiments included tensile tests and differential scanning calorimetry (DSC). The addition of the plasma treated nano titanium dioxide particles into PP/PLA caused a change in Young's modulus and yield stress of the composites. Strain rate sensitivity of the PTNTOPPCF changed as plasma with and without oxygen treated nano titanium dioxide particles was added to it with different percentage of weight. It was increased with more PLA, MAH, and higher flow rate of oxygen. Activation volumes ranged in 4−40(nm)3 for true nanocrystalline material estimated by the Eyring equation, which were changed un-monotonically with oxygen plasma treatment.