Advanced Materials Research Vols. 194-196

Abstract: Synthesis of carbon nanofibers from V-type pyrolysis flame is a novel method. It needs simple laboratory equipments and normal atmosphere pressure. The V-type pyrolysis flame experimental system is introduced. Carbon source is the carbon monoxide and heat source is from acetylene/air premixed flame. Pentacarbonyl iron is served as catalyst. The carbon nanofibers were characterized by scanning electron microscope and transmission electron microscope. This study aims to examine temperature condition for carbon nanofibers formation in pyrolysis flame and to characterize its morphology and structure. The carbon nanofibers with less impurity were captured successfully in the V-type pyrolysis flame. The diameter of carbon nanofibers was approximate between 100nm and 200nm, and its length was dozens of microns. When the temperature was below 750°С , the growth of carbon nanofibers came into the preparation growth period. The length of the carbon nanofibers increased gradually and the diameter had no obvious change with the raising of temperature. When the temperature was above 750°C, the growth of carbon nanofibers came into the exuberant growth period. The growth of carbon nanofibers was finished when the temperature was above 820°С . Higher temperature was meaningless after the carbon nanofibers formation. The contrast experiments show that it is the most favorable to form carbon nanofibers when the temperature is from 750°С to 850°С .

Abstract: Rabbit hair is an important animal fiber in China, making up 90% of the total output in the world. Fuds is one of familiar problems in the processing of rabbit hair, which lead to plenty of waste fibers. Recently, there has been interest in converting protein fibers into powder to develop their new uses. This provides great opportunities for waste rabbit hair. In this study, rabbit hair powders have been produced and the structure and properties were characterized at multi-level. Surface morphology of rabbit hair powders was observed by scanning electron microscopy (SEM) and the majority of rabbit hair powders appear to be small fibrous particles. The FTIR spectrum of rabbit hair and rabbit hair powders was detected. Although no new chemical bonds were produced in the rabbit hair powders, the result showed that some absorbing peaks of rabbit hair powder become stronger than that of rabbit hair. Absorption of rabbit hair powders was also investigated. The result showed that rabbit hair powder had higher moisture retention rate than that of rabbit hair, wool fiber and cotton fiber. Moreover, rabbit hair powder showed remarkable sorption ability for metal ions. The characterization of rabbit hair powder will provide useful basal data for the further application of rabbit hair in novel areas.

Abstract: In this essay, the effects of grain refinement on corrosion behavior and hardness of equal-channel-angular-pressed (ECAPed) AISI 304 austenitic SS were studied. Finer grains with average size of 5μm in the specimen were obtained after four ECAPed passes compared with as-received one with grain size in range of 55μm Strain-induced grain refinement process can increase grain boundary and dislocation. Thus, the corrosion resistance of ECAPed AISI 304 austenitic SS would be improved.The refined microstructure achieves more positive open circuit potential (OCP) and lower corrosion current density in polarization corrosion tests.Through this process, austenitic stainless steel with better performance in corrosion resistance can be gained.

Abstract: We present a strategy to fabricate discrete Au nanorods (AuNRs) into controllable side-by-side (SS) and end-to-end (EE) assemblies through bio-recognition of h-IgG and anti-hIgG Fab. Due to anisotropic properties of AuNRs, bifunctional PEG (SH-PEG-COOH) with low concentration preferentially bound to the ends of AuNRs while high concentration and large amount resulted in binding on the side surfaces and then proteins were covalently conjugated to either surface through EDC/NHS. Thus, controllable SS and EE assembly of AuNRs were obtained through antibody-antigen recognition.

Abstract: Magnesium-based hydrogen-storage materials were prepared by reactive ball-milling under hydrogen atmosphere. It was shown that crystallitic carbon from anthracite carbonization was an effective milling aid for magnesium. Dispersive nano-particles about 20 to 60 nm were prepared from magnesium with 35 wt.% of crystallitic carbon additive by milling for 3 h under 1 MPa of hy-drogen atmosphere. The magnesium hydrided into MgH2 and the crystallitic carbon was endowed with C=CH₂ functional group during milling. The hydrogen-storage materials were used for the hy-drodesulfurization of CS₂ and thiophene, and H₂S and MgS yielded after reaction. To add molybdenum into the hydrogen-storage materials was in favor of the hydrogenation of sulfo-compounds.

Abstract: The dense layered ternary Ti₂AlN ceramics were successfully synthesized by a combination of mechanical alloying and hot press sintering from the mixture of Ti and Al in nitrogen milling atmosphere. The phase transformation and morphology characteristics in mechanical alloying and subsequently hot press sintering were studied by using XRD and SEM as well as EDS. The results show that Ti(Al,N) amorphous powders were synthesized successfully by mechanical alloying. When the as milled powders were hot pressed at 1200 °C for 1 h, full dense and highly pure layered ternary Ti₂AlN ceramic was synthesized.

Abstract: Three different kinds of zinc oxide (ZnO) nanostructure films have been synthesized on an indium tin oxide (ITO) glass substrate by electrochemical method with adjusting the concentration of the electrolyte, deposition time and temperature. X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM) and photoluminescence (PL) spectrum have been used to determine the characteristics of these nanostructures. The results show that concentration of the electrolyte is one of the most important factors that determine the morphologies of ZnO films. Nanobuds, nanorods, flakes are obtained with the electrolyte concentration increasing. Nanobuds and nanorods have no significant changes with the deposition time prolonged while the flakes grow bigger and thicker. The flakes merge together at high temperature while nanobuds remain unchanged except getting larger and sparser. Nanobuds and nanorods show single crystal patterns while the flakes are composted by multi crystals. The reasons forming such different morphology were discussed according to crystal growth theory. The PL spectra of these ZnO films are quite different according to various microstructures. The film with flake structure has a significant widen near edge emission peak with the depressed visible emission, which may have potential applications on optoelectronic devices and sensors.

Abstract: We present a discussion of the size-, potential-dependence of the confinement energy in the nanostructure, as well the blue shift due to quantum confinement effect. In this case, we solve the Schrödinger equation by employing two simple models with one-dimensional periodic crystal potential. Results show that the confinement energy increases abruptly as the size of nanostructures decreases. Importantly, the confinement energy no longer strictly follows the size-dependent inverse square formula given by Brus. Furthermore, the band gap and blue shift depend on the crystal potential in the nanostructure, and the confinement energy decreases with the increase of the potential. We also find that the surface bond constriction plays an important role of the confinement energy.

Abstract: Carbon nanotubes(CNTs) with uniform wall thickness were synthesized by a solid-liquid reaction route. Calcium carbide block and carbon tetrachloride as double carbon sources were enclosed in a 100ml stainless steel autoclave at 400°C for 8 hours. The fabricated products were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), and Transmission electron microscope (TEM). The research results indicate that the synthesized CNTs have lengths on the order of 10μm and external diameters in the range of 120-200nm. The nanotubes are typically the uniform inner diameters of 70nm and grow in the same direction. The growth mechanism is simply discussed.

Abstract: Titania nanotubes (TNTs) have been successfully synthesized by hydrothermal treatment of anatase TiO₂ powder in NaOH solution at 110°C for 90 hours and then annealed at the temperature of 400°C. The morphology and crystalline structure of the nanotubes were characterized by using transmission electron microscopy (TEM) and X-ray diffraction (XRD). The average specific surface area of the particle was probed using gas adsorption-desorption measurements, and average particle size was calculated from the specific surface area. Based on the microscopic observations on the transformation process, it indicated that the formation of nanotubular products remained in their shape after the annealing process. While XRD results confirmed the nanotubes were composed of pure anatase TiO₂ nanoparticles.