Advanced Materials Research Vols. 821-822

Abstract: Activated carbons are prepared from hemp stem with KOH as activating agent under different ratio of KOH to carbon conditions. The BET(Brunauer Emmett and Teller) specific surface area of the hemp stem-based activated carbons first increases and then decreases with the increasing ratio of KOH to carbon. The specific surface area, micropore surface area and volume of the activated carbons reach a maximum of 1589.27m²/g 1420.52m²/g, 89% of the total area, 0.751m³/g at the ratio of 4.5:1. The micropore size distribution shows the activated carbons contain a large number of ultramicropore and supermicropore.

Abstract: Ni-Fe layered double hydroxide containing carbonate anion (CO₃^2- ) has been successfully synthesized by a process of homogeneous precipitation involving urea hydrolysis under hydrothermal conditions. Factors that influence the composition and the crystallinity degree of NiFe-LDH, such as the molar fraction of urea/NO₃^- in solution, the total metal ion concentration in solution and the aging time, have been investigated in detail. Structure and morphology of the sample were characterized by X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) spectra and scanning electron microscope (SEM). The results indicate NiFe-LDH with high purity present well-crystalline, uniform crystallite size

Abstract: Porous α-alumina supports were seeded with monodisperse nanocrystalline HZSM-5 zeolite and calcined. The supports were treated in a synthesis solution to grow the seeds into HZSM-5 membrane with aluminum nitrate (Al (NO₃)₃), tetraethyl orthosilicate (TEOS), and tetrapropyl ammonium hydroxide (TPAOH) as raw materials. X-ray diffraction (XRD) characterization results showed that the membranes consisted of well-crystallizedH ZSM-5. The influence of crystallization time on morphology of HZSM-5 membranes was represented by scanning electronic microscopy (SEM) characterization: the HZSM-5 zeolite membranes on the supports were defect free and the membrane thickness was increased with the crystallization time prolonged.

Abstract: Electrospinning is a process that fabricates continuous fibers with diameters in the nanoto micron range. Pullulan with different concentrations were successfully electrospun into nanofibers with water as solvent in this study. We have evaluated the effects of solution concentration on the morphology of the fibers. The morphologies of the nanofibrous mats were examined by Scanning Electron Microscopy (SEM). With increasing the solution concentration, the electrospun nanofibers changed from beaded nanofibers to smooth nanofibers, meanwhile, the average diameters of electrospun pullulan nanofibers increased from 44nm, 89nm, 136nm, 172nm to 219nm when the solution concentration changed from 12, 15, 20, 25 to 30 wt%. The distribution of electrospun fibers is normal distribution. The electrospun nanofibrous mats will be a promising food package material.

Abstract: In this paper, a novel tubular scaffold was constructed by electrospinning technique and rolling method. Firstly, a high speed rotation drum was used to collect aligned poly (lactic acid) (PLA) nanofibers. Secondly, the membrane was cut and rolled into tube. Finally, a randomly oriented nanofibers layer was electrospun onto the rolled tube to envelope the end of rolled membrane and increase the mechanical properties. The morphology and alignment of nanofibers was observed and the mechanical properties were evaluated. The results showed that desirable alignment could be obtained by adjusting rotation speed. Along the fiber direction, the tensile stress of aligned PLA nanofibers membrane reached 49.32 ± 14.83 MPa and the elongation was17.71% ± 0.06%. The suture strength was more than adequate for suturing during implantation (2.36 ± 0.80 N/needle). This results derived from this study indicated that the construction technology was feasible and fundamentally verified the applicability of novelly designed scaffolds in tissue engineering.

Abstract: A series of catalysts made of ruthenium loaded on γ-Al₂O₃ and γ-Al₂O₃ nanorods were tested for hydrogenation CO₂ to formic acid. Among these catalysts, the catalyst 2% Ru/Al (n) gave the highest activity for hydrogenation CO₂ reaction with the yield of formic acid up to 13.6 mmol /h. The excellent catalytic activity is related to the highly dispersed ruthenium species on the surface of support and abundant hydroxyl groups of the support. The dispersion of ruthenium species and the hydroxyl groups of supports were studied by characterization of XRD, nitrogen adsorption measurement, TEM, D₂/exchange and H₂-TPR in detail. The γ-Al₂O₃ nanorods lead to the highly dispersed ruthenium species and abundant hydroxyl groups, which appears to be more effective for hydrogenation CO₂ to formic acid.

Abstract: Within the frame of two-phase superparamagnetic nanoparticles the effect of magnetic and geometric properties of superparamagnetic nanoparicles on the time of their magnetic relaxation has been defined. With increasing of volume, elongation of nanoparticle and relative volume of inclusions the time of relaxation grows rapidly. Metastability conditions of magnetic states have been developed. Growth of exchange constant magnitude of interphase interaction results in increasing of relaxation time regardless of exchange constant sign. Keywords: superparamagnetic particles, core-shell nanoparticles, relaxation time, magnetic states, critical field, metastable magnetic states, interphase exchange interaction.

Abstract: Micron-sized Mg (OH)₂ particles were synthesized by precipitation of MgSO₄ with gaseous ammonia. An experimental design procedure was used to investigate the effects of the concentration of MgSO₄, temperature of the reaction, time of the reaction, assembly time, speed of stirring, ultraphonic, the introduce of NaOH and surfactant on the mean particle size and the particle size distribution. Laser particle size analyzer, XRD, TG-DTG, SEM and other instrument was used to characterize the product and corresponding particle size.

Abstract: Ag-doped nano-TiO₂ sol was prepared at a low temperature and was used to finishing cotton fabrics, and observed the crystal structure and the dispersion of nano-TiO₂ on the fabric by X-ray diffraction (XRD) and scanning electron microscope (SEM); Discussed the influence of different amount of silver on antibacterial properties; Studied the impact of different finishing methods on UV resistance performance as well as the degradation of methylene blue and VOC performance. Results showed that Ag-doped nano-TiO₂ on the fabric which was finished by steaming method with the sol agent were anatase phase,and its particle size was 20-40 nm, when the molar ratio of tetrabutyl titanate and silver nitrate was 70:1, the Bacteriostatic rate was 99.9%, and fastness to washing was well, UV resistance and degradation of MB and VOC performance had greatly ascended, and less influence on the fabric performance.

Abstract: Slow-released anti-mosquito microcapsules finishing agent was prepared using the resin of melamine-formaldehyde as wall and DEET as core by in-situ polymerization. The effects of emulsifier content and oil/water ratio on anti-mosquito finishing agent were investigated. Scanning electron microscopy (SEM) and laser particle size analyzer were employed to characterize the microcapsules. The optimum synthesis condition was: 3% emulsifier SMA and oil/water ratio at 4:17. Under the conditions, the mean particle size of the capsules was about 39μm.