Abstract: In this paper, TiH2-47Al-5Nb (at.%) and TiH2-47Al-7Nb(at.%) alloys were mixed and synthesized using TiH2, Al and Nb powders. The composition and morphology evolution of the mixed powder were systematically investigated during high energy ball milling. The results show obvious that structure change of the particle during milling, and amorphous, TiAl, Ti3Al and Ti2Al phases at nanoscale are formed. The addition of Nb shows an active influence on the decomposition of TiH2 and formation of TiAl-intermetallics. Compare with Ti-Al system alloy, the forming process of TiAl-intermetallics for TiH2-Al-Nb system alloy is different and slower. Ti2Al metastable phase formed after ball milling for 15 h in our experiments.
Abstract: Synthesis carbon nanofibers from V-type pyrolysis flame use simple carbon monoxide and acetylene /air premixed flame. Catalyst is transported by helium into the burner. The carbon nanofibers from the sampling probe were characterized by scanning electron microscope and transmission electron microscope. The influence of the fuel equivalence ratio and the flow of carbon monoxide were discussed in detail to reveal the formation rule of carbon nanofiber from the pyrolysis flame. The results indicate that carbon monoxide is a good carbon source gas for the preparation of carbon nanofibers. Under appropriate temperature and optimized flow of carbon monoxide, carbon nanofibers with good quality can be prepared from the V-type pyrolysis flame. It can be concluded that this flame method is effective for the preparation of carbon nanofibers.
Abstract: Low-pressure chemical vapor deposition (LP-CVD) technique has been utilized for controlled growth of carbon nanotube (CNT) arrays on silicon wafers. The tube-diameters of CNTs and the number of graphene layers are controlled by varying the thickness of catalyst films. The catalyst particle density and the growth conditions such as the ambient gas and the local environment are all crucial for the formation of vertically aligned CNT arrays. The length of CNT arrays can be controlled by altering the growth time. In addition, the supercapacitive properties of CNT arrays with various morphologies growing on different current collectors have been investigated using a less corrosive 0.5 M Na2SO4 aqueous solution as the electrolyte. Vertically aligned CNT arrays on Ti-Si substrate produce a higher capacitance compared to randomly oriented CNTs on the same current collector. Furthermore, Ni foam enables better utilization of active materials than Ti-Si substrate. CNT arrays electrodes fabricated by this simple, low cost approach demonstrate stable and consistent capacitor behaviors for a wide range of scan rates. Moreover, CNT arrays electrodes provide better platform for further integration with transitional metal oxide, via simple sputtering or electrodeposition technique, to enhance the supercapacitive performance.
Abstract: Schistose and aciculate CuO nanostructures have been synthesized by a novel ammonia assisted hydrothermal method of copper alginate. The conversion processes of copper alginate are investigated by thermogravimetrics (TG) analyses under N2 and air atmosphere. The morphology, structure, and composition of the obtained CuO are investigated using SEM,TEM and XRD. It is found that different temperature and pH value resulted in the morphology and structure evolution of CuO. Ammonia was used as structure-directing agent in the hydrothermal system. The aggregation state of the nanostructures was controlled by the temperature. Dispersive schistose structures about 1μm in diameter were synthesized with 0.5mL ammonia at different temperatures. Dispersive microspheres of about 4 μm in diameter were also synthesized with 1 mL ammonia. Microspheres composed of nanoneedles and nanoplates were synthesized at 120°C and 160°C, respectively. Moreover, a possible growth mechanism governing the formation of such a nanomicrostructure was primarily discussed.
Abstract: To examine the effects of morphologies of one-dimentional metal oxides on their surface properties, two typical morphologies of manganese dioxide (one is nanorod, the other is nanofiber) as a model of metal oxide were prepared with hydrothermal approach under similar conditions. The adsorption properties of Pb2+ in aqueous solution were carried out by using surface active group of MnO2 with different morphologies. The results indicated that the sorption capacities for Pb2+ were dramaticly increased via tailoring the morphology of MnO2. The products were characterized with SEM (Scanning Electron Microscopy), XRD (X-ray Diffraction), FTIR (Fourier-Transform Infrared), atomic absorption spectrophotometer, and so on. These results illustrated that it was feasible to improve the removal efficiency of heavy metal ions dramatically in aqueous solution by tailoring the morphology of nanostructured MnO2.
Abstract: Nanostructured manganese oxides (Mn3O4, MnOOH) were successfully prepared by a hydrothermal method using MnCl2 as manganese source, NaOH as precipitation agent and H2O2 as oxidant. The composition and morphology of the products were determined by the dripping speed of NaOH solution, the adding order of reactant and the hydrothermal time. Single phase of Mn3O4 nanoparticles can be prepared by dropwise addition of the NaOH solution to the solution of MnCl2 and H2O2. While single phase of MnOOH nanorods can be obtained by pouring the NaOH solution into the reaction system quickly or changing the adding order of NaOH and H2O2. When the dripping speed of NaOH solution was 6mL/min, and an appropriate amount of surfactant (C18H29NaO3S) was added, Mn3O4 nanorods can be obtained. The hydrothermal method can be readily controlled to synthesize Mn3O4 and MnOOH with different morphologies. The Mn3O4 sample had higher capacitance than the MnOOH sample. The morphologies of these samples had little effect on their electrochemical performance.
Abstract: The grown in situ carbon nanotube chemically modified electrode (GSCNT-CME) was prepared by growing carbon nanotube (CNT) in situ on the pretreated graphite electrode (GE) via a liquid ethanol ﬂame. The GSCNT-CME was applied to detect the trace copper in water. The researching results showed that the GSCNT-CME has good electrochemical detection sensitivity and accuracy in the detection of trace copper in water.
Abstract: Functionalized carbon nanotubes (CNTs) composite nanofibers with high melting point polyurethane (PUH) as matrix were fabricated by electrospinning method, which were later stacked alternately with low melting point polyurethane (PUL) films into composite nanofiber reinforced composites through a hot press treatment. The tensile modulus (30 wt.% composite nanofibers) reaches 54.3 MPa, 187% higher than that pure PUL film.
Abstract: Based on the growth kinetics of the SiO2 particles, we studied the kinetic hetero-precipitation process on the interface of polystyrene (PS) microscale particles. The nanoscale SiO2 shell thickness increased with increasing time and was proportional to the square root of the initial concentration of TEOS precursor while governed by hetero-precipitation process. Moreover, the hetero-precipitation process followed the first-order growth mechanism of silica onto the surface of templating PS pariticles. Properly controlling the reagent concentrations could alleviate and even avoid, to a certain extent, aggregation among PS@SiO2 particles that could otherwise have an adverse effect on the properties and applications of those composite particles and the corresponding SiO2 hollow products.