Papers by Author: Quan Ji

Abstract: Cellulose-insoluble silicate (talcum powder) hybrid fibers with 10%, 20%, 30% silica contents were prepared by wet spinning. The flammabilities and combustion processes were evaluated by the limiting oxygen index (LOI) and cone calorimetry. The LOI results suggested that the hybrid fibers were flame retandant with the LOI value of 22, 25 and 27, as compared to 20 of pure cellulose fibers. Cone calorimetry showed that the rate of heat release value and total heat release value of hybrid fibers decreased. Hybrid fibers with 20% SiO₂ loading is the best flame retardant sample. SEM studies of residues after cone calorimetry indicated that the hybrid fibers produced tight and hard residue crusts.

Abstract: We have investigated the effect of zirconium oxide on the thermal degradation and flame retardancy of viscose fibers. ZrO₂/cellulose fiber was prepared by wet spinning. Combustion behaviour and flammability were assessed using the limiting oxygen index (LOI) and thermogravimetric analysis from ambient temperature to 800°C and cone calorimetry. LOI results showed that the ZrO₂ increased the LOI of viscose fiber from 20% to 26%, which showed that ZrO₂ particles had a positive effect on cellulose flame-retardancy. Results from thermogravimetric analysis (TG) indicated that the ZrO₂/cellulose fibers produced greater quantities of residues than viscose fibers. The combustion residues were examined using the scanning electron microscopy, indicating that ZrO₂/cellulose fiber produced consistent, thick residues. Cone calorimetry indicated that heat release rate and total heat release values of ZrO₂/cellulose fiber were less than those of viscose fibers.

Abstract: Experimental research on calcium alginate fibers thermal degradation and flame retardancy under catalysis of metallic salts was done by limiting oxygen index (LOI), scanning electron microscopy (SEM), and thermogravimetric analysis (TG) methods. LOI results show that with increasing calcium ions content, the flame retardant properties of the calcium alginate fibers improves further. The residues of calcium alginate fibers gradually retained fiber shape and on the surface of the residues the holes reduced, with the calcium ion content increasing. TG indicates temperature at maximum rate of weight loss (T-max) was clearly shifted from 246 °C for alginic acid fibers to 244°C, 236°C, 208°C, 205 °C and 203°C (SCa-1-1# calcium alginate fibers, SCa-2-2# calcium alginate fibers, SCa-3-3# calcium alginate fibers, SCa-4-4# calcium alginate fibers, SCa-5-5# calcium alginate fibers), respectively. The thermal degradation residues at 1000°C for different calcium alginate fibers are 13.7%, 16.1%, 17.2%, 18.2%, 18.4%, 19.2%, separately. Further discussion of the combustion process and flame retardant mechanism is presented.

Abstract: Fluorocarbon coatings were deposited on the surface of regenerated cellulose films by RF magnetron sputtering, using polytetrafluoroethylene targets. Argon was used as the working gas. The coatings were characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, atomic force microscopy, and static contact angle and oxygen permeability measurements. It was found that the coatings were made up of the four components -CF3, -CF2-, -CF- and -C-. The [F]/[C] ratio varied with sputtering conditions. The static contact angle of the coatings was greater than 90° at lower power and higher pressure, and the substrate material was transformed from hydrophilic to hydrophobic character. The fluorocarbon coatings were porous and did not influence the oxygen permeability of the cellulose film substrates.

Abstract: In this paper, ferric alginate fibers was prepared by wet spinning of sodium alginate into a coagulating bath containing ferric chloride. The carbon-supported nanoscale zero-valent iron fibers (CSNZVIF) were obtained through thermal degradation of ferric alginate fiber at 900°Cunder N₂ atmosphere. The product was characterized by field emission scanning electron microscopy (FESEM), X-ray power diffractometer (XRD), and Brunauer-Emmett-Teller (BET) surface area. It was found that zerovalent iron particles were well dispersed in the amorphous carbon fibers. CSNZVIF has high surface areas of 352 m²/g. The existence of carboxylic group and hydroxyl group in ferric alginate structure unit plays key role in the formation of carbon-supported nanoscale zero-valent iron fibers. Fe³⁺ was reduced to Fe⁰ by hydroxyl group and as-formed amorphous carbon during heating under N₂. This thermal degradation and self-reduction reaction of ferric alginate fiber is potentially scalable to large production and continuous processing for preparing CSNZVIF.

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: A series of novel transparent hydrophobic regenerated cellulose (RC) films were coated with a fluorocarbon polymer by radio frequency magnetron sputtering. The effect of sputtering power and pressure on the surface morphology, chemical composition, contact angle and visible light transmittance of the coated films were investigated by atomic force microscopy, X-ray photoelectron spectroscopy, contact angles and ultraviolet-visible spectroscopy. The surface roughness increased as the sputtering power and pressure increased. The fluorocarbon coatings contained four components: -CF₃, -CF₂-, -CF- and -C-. The relative proportions of the saturated components significantly affected the hydrophobicity of the coatings. After applying a fluorocarbon coating, the static contact angle of the coatings was greater than 90°, and the substrate RC film was transformed from hydrophilic to hydrophobic. The visible light transmittance was greater than 80% when the roughness of the coating was less than 100 nm. The optimal sputtering conditions used a power between 80 and 150 W, and pressure between 1.0 and 3.0 Pa.

Abstract: The target-substrate distance has a significant effect on the morphology and the relative deposition rate of fluorocarbon films deposited by RF magnetron sputtering. The films were deposited on regenerated cellulose substrate using a polytetrafluoroethylene (PTFE) target, with argon as the working gas. The surface and fracture cross-section morphologies of the deposited films were examined by scanning electron microscopy (SEM). The average thickness of the fluorocarbon films and the relative deposition rates were calculated for varying target-substrate distances. The films had island-like structures composed of nanoscale particles, and the surfaces were not flat. The density of the particles increased and their size decreased with increase of the target-substrate distance in the range 30 to 80 mm. The relative deposition rate increased at first and then decreased with increased target-substrate distance: the optimal target-substrate distance was 50-60 mm.

Abstract: Nanowire-mesoporous network structured fluorocarbon polymer films were prepared by radio-frequency (RF) magnetron sputtering of a polytetrafluoroethylene (PTFE) target on a poly(ethylene terephthalate) (PET) substrate. The fluorocarbon films were used as precursor materials to prepare fluorocarbon/ZnO double-layered hybrid films by reaction sputtering of a Zn target on the fluorocarbon films. The hybrid films had strong UV absorption that was far larger than the sum of the individual absorptions of fluorocarbon film and ZnO film because of a synergistic effect. The hybrid films exhibited multi-enhanced ultraviolet absorption due to the π-conjugated molecular structure, the nanoparticle-mesoporous reflection of fluorocarbon polymer films, and the absorption effect of nanosized ZnO particles.

Abstract: Nano size silver films were deposited on the surface of regenerated cellulose films by magnetron sputtering, to impart antibacterial functionality to the cellulose films. Field emission scanning electron microscopy (FESEM) images revealed that the silver films were composed of nano size compact grains and the surface shape of the grains changed with changing sputtering power. As the power increased, the size of the nano silver grains increased and the number of grains decreased. Surface elemental analysis by energy dispersive spectrometry (EDS) showed a small amount of elemental silver on the surface. The antibacterial activity of the films was assessed by the shake flask test which measured the number of Staphylococcus aureus bacteria. The percentage reduction of the bacteria reached >99.9%.