Mu-Rong Yang

The Doping Effect on the Electrochemical Properties of LiFe0.95M0.05PO4 (M = Mg2 + , Ni2 + , Al3 + , or V3 + ) as Cathode Materials for Lithium-Ion Cells

Mg 2+ , Ni 2+ , Al 3+ , or V 3+ ion with an atomic radius similar to or smaller than that of Fe 2+ ion was doped into the Fe site to synthesize LiFe 0.95 M 0.05 PO 4 samples using a solution method. The mean particle size of all samples, independent of doping species, was about 6 ± 0.5 μm. All samples in this study contain a carbon content of about 3 wt % and have a similar Brunauer-Emmett-Teller surface area (about 18-20.5 m 2 g -1 ). The synergetic effect of the supervalency and larger atomic size of the doping element will induce the lattice expansion and Li-O bond lengthening of the olivine structure. The lengthening and weakening of the Li-O bond will be beneficial to the electrochemical performance of cathode materials especially under the high C rate. Hence, the Life 0.95 V 0.05 PO 4 powder with the largest volume of unit cells (longest Li-O bond length) exhibits the highest discharging capacity of 152 and 136 mAh g -1 at C/10 and 1C rates, respectively.

The antibacterial activities of hydrophilic-modified nonwoven PET

Abstract The hydrophobic surface of nonwoven PET with surface inertia has limited the practical bioapplications. In this study, nonwoven PET was activated by argon gas plasma and subsequently water-soluble monomers (acrylamide and itaconic acid) were grafted onto the PET by UV-induced surface graft polymerization. After the plasma activation and/or grafting, the hydrophobic surface of nonwoven was modified into a hydrophilic surface. To improve wound healing, the following three biocides have been used in this study: (1) AgNO3 solution complexes, (2) Vinyl quarternary ammonium salt (VQAS) and (3) chitosan. For Ag+ ion impregnation and VQAS grafting, the amount of these biocidal materials on the surface increases when the monomer concentration increases. However, for the chitosan immobilization, the chitosan amounts seemingly decrease with an increase in the chitosan concentration. For biocidal properties, the Ag+ ions produce best result. However, the VQAS grafting is most durable against the flushing water.

Effects of additives on the photo-induced grafting polymerization of N-isopropylacrylamide gel onto PET film and PP nonwoven fabric surface

Abstract In this study, the thermosensitive gels were grafted onto plasma-activated polyethylene terephthalate (PET) film and polypropylene (PP) nonwoven fabric surface. The Ar* plasma pretreatment was carried out and subsequent photo-induced surface graft polymerization was employed to graft the N-isopropylacrylamide (NIPAAm). The effects of additives during the grafting were accessed. The additives used were ammonium peroxodisulfate (APS, initiator), N,N,N′,N′-tetra-methylethylene-diamine (TEMED, promoter) and N,N′-methylenebisacrylamide (NMBA, cross-linking agent). The results indicate that the additives of APS, TEMED and NMBA will be beneficial in promoting the grafting. The additives, including all three, will give the best result. These grafted gels exhibit a lower critical solution temperature (LCST) at about 32 °C, which shows that the temperature-responsive behavior of bulk P (NIPAAm) hydrogel was preserved.

The improvement of high-temperature oxidation of Ti–50Al by anodic coating in the phosphoric acid

Abstract The high temperature cyclic oxidation resistance of Ti–50Al can be improved by anodic coating in phosphoric acid aqueous solution (4 wt% H 3 PO 4 ) at 18°C. Sparking occurs sporadically on the surface as the voltage is over 300 V and the instantaneous current density after 45 min of anodization increases with increasing voltage. The anodic films are amorphous and contain substantial amount of phosphorus. Cyclic oxidation test indicates that the anodization can remarkably reduce the oxidation in air at 800°C and the improvement increases with increasing anodizing voltage up to 400 V, at which the parabolic oxidation rate constant can be reduced to about 1/600 of that for as-homogenized Ti–50Al. Raman spectra show that the anodic film can slow down the formation of rutile and α-Al 2 O 3 during oxidation. The doping effect of phosphorus ions in titanium oxide accounts for the improvement of high temperature oxidation of Ti–50Al.

Wettability and lubrication of polytetrafluorethylene (PTFE) by UV-induced graft copolymerization on plasma-treated surface

Abstract Wettability of PTFE has been investigated by grafting the hydrophilic monomer, acrylamide (AAm). The stable PTFE needs to be activated before grafting. These active sites for further photo-graft polymerization can be provided on the surface of PTFE by an argon plasma (Ar*) or by the introduction of a plasma-deposited HMDSZ layer. Grafting AAm on Ar*-treated PTFE will improve its wettability for θ from 101 to 33 ° without worsening its low friction coefficient characteristic, about 0.27 for the coefficient of friction against a glass plate in a wet state. Owing to the general characteristics of plasma deposited film, the plasma-deposited HMDSZ layer will provide a smooth substrate with peroxides for further grafting. Therefore, grafting AAm on HMDSZ plasma deposited on PTFE will not only modify the surface from hydrophobic to hydrophilic surface but also reduce the friction coefficient to as low as 0.1.

Photoluminescence of ZnS: Sm phosphor prepared in a reductive atmosphere

Abstract The characteristic emission of Sm +3 in Zn phosphors, fired in inert atmosphere (N 2 gas) at various temperatures, was not detected. However, fired in reductive atmosphere at 1050°C, the characteristic Sm +3 emission appears, which exhibits intra-4f transitions at 570, 606 and 653 nm, as predicted from the 4 G 5/2 level to the 6 H 5/2 , 6 H 7/2 and 6 H 9/2 levels. Sm doping favors the formation of hexagonal phase in host lattice of ZnS:Sm. The increase in hexagonal phase content will boost the overall photoluminescence emission intensity. The self-activated luminescence intensity increases with the increase in the amount of Sm doping up to a maximum at 0.2 mol% of Sm dopant. According to the phase identification by X-ray diffraction, the Sm 2 O 2 S phase favors the Sm +3 characteristic luminescence but it deteriorates in Sm 2 O 3 .

The interaction between blood and the surface characteristics of plasma polymerized films

The chemical structure and blood clotting time of plasma polymerized films prepared from cyclohexane, perfluorotributylamine (FC-43), and hexamethyldisilazane (HMDSZ) were investigated. Plasma polymerization was conducted in an internal-parallel-electrode type bell-jar reactor system. Chemical structure of plasma polymerized film was similar to that of original monomers, but new groups were formed due to oxygen incorporation during or after plasma process. The surface with a low dispersive and polar component of the surface energy is beneficial to the blood biocompatibility. Even at lower power level, chemical structure of the plasma film is also influenced by substrates. The best plasma-operating conditions for a better blood compatibility are plasma FC-43 on PVC and plasma HMDSZ on PE under 20 W 100 mTorr. However, a better result can be obtained by changing the plasma itself, and a blood clotting time of 2.3 times that of glass can be reached for FC-43 on PE.

DC plasma-polymerized hexamethyldisilazane coatings of an equiatomic TiNi shape memory alloy

Abstract The TiNi corrosion resistance of Ti 50 Ni 50 shape memory alloy can be substantially improved by DC plasma-polymerized hexamethyldisilazane (PHMDSN) coatings. The initial PHMDSN deposition rate increases with increasing DC voltage. The deposition rate decreases gradually with time until the glow discharge is extinguished. The higher DC voltage used in plasma polymerization will develop a film with a more inorganic nature from the IR spectrum analysis and water contact angle measurements. The PHMDSN coatings for DC voltage ≥1000 V are protection against the corrosion in Ringer’s solution and can be deformed up to a 2% strain. The corrosion current density of the TiNi alloy can be lowered by as many as four orders of magnitude. The pitting potential and re-passivation potential can also be enhanced to nobler potential after PHMDSN coatings. The widely scattered pitting potential of the as-homogenized TiNi can also be improved by the PHMDSN coatings.

Oxidation Behavior and Oxide Layers of Ti–50Al Intermetallics by Preoxidation in High-Pressure Oxygen

The oxidation resistance of Ti–50Al intermetallics is improved bypreoxidation for 1, 4, or 16 hours in high-pressure, pure oxygen(≈3.9 atm) at 900°C. Specimens preoxidized for 1 hr exhibit betteroxidation resistance than others. Prolonged preoxidation time candeteriorate the oxidation resistance and reduce the parabolic-lineartransition time during subsequent cyclic oxidation in 800°C air. Theoxide-mound occurrence is an important factor for evaluating theeffectiveness of the preoxidation treatment in oxygen. The formationmechanism of Z-phase (Ti5Al3O2) in the Al-depleted layer beneath theflat oxide scale and that beneath the oxide mound are also proposed inthis study.

Effect of LiCl flux on the red ZnS:Sm phosphors fired in reductive atmosphere

Abstract ZnS:Sm phosphors with strong red emission can be prepared by solid state reaction fired in a reductive atmosphere. Using LiCl as the fluxing agent favors the crystal growth of ZnS as well as increasing the content of the hexagonal phase in ZnS. The higher content of the hexagonal phase and evenly-distributed samarium compound on ZnS can induce greater light energy absorption and result in better photoluminescence emission intensity and color purity. The red emission intensity of ZnS:Sm phosphors is increased about 5 times with the addition of LiCl flux agent compared with the addition of Sm alone without any flux agent. The optimal concentration of LiCl flux is 2.0 mol% for ZnS with doping 0.2 mol% Sm phosphors fired in a reductive atmosphere.