Yuanlin Ren

A new method for preparing alumina nanofibers by electrospinning technology

A new method for synthesizing alumina (Al2O3) nanofibers through the electrospinning method was reported. The spinning solutions of anhydrous aluminium chloride/polyvinylpyrrolidone (AlCl3/PVP), wh...A new method for synthesizing alumina (Al2O3) nanofibers through the electrospinning method was reported. The spinning solutions of anhydrous aluminium chloride/polyvinylpyrrolidone (AlCl3/PVP), which were prepared by the sol-gel process of the mixture of AlCl3, PVP, ethanol and redistilled water, were electrospun to form AlCl3/PVP organic-inorganic hybrid fibers. Alumina nanofibers with average diameters of 100—800 nm were obtained by calcinations of the as-prepared fibers. The fibers were characterized by SEM, TG-DTA, FTIR, XPS and XRD. The results showed that with the increase of the concentration of spinning solution, the diameter of fibers also increased, and that the diameter of fibers decreased with the increase of the applied voltage and calcination temperature. The uncrystalline Al2O3, γ-Al 2O3 and α-Al2O3 were obtained after calcinations of about 5 h at 450, 900 and 1100°C, respectively.

Phosphorus-doped organic–inorganic hybrid silicon coating for improving fire retardancy of polyacrylonitrile fabric

In this study, in order to increase the flame retardancy of polyacrylonitrile fiber fabric, an organic–inorganic hybrid silane coating doped with polyphosphoric acid was prepared using tetraethoxysilane as the precursor by sol–gel technique. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscope confirm the successful silicon and phosphorus-doped silicon coating on polyacrylonitrile fabric. Obviously, the char residue values at 800 °C of the silica-coated and phosphorus-doped silica coated polyacrylonitrile fabric samples were observed to increase 17.93 and 25.92%, respectively than that of the control sample. The peak and total heat releases of the phosphorus-doped silica coated polyacrylonitrile fabric significantly reduced to only 44.9 and 42.1% of that of polyacrylonitrile fabric, respectively. Besides, both the peak values of smoke production rate and total smoke production are remarkably reduced. The results show that the coated layer can effectively improve the thermal stability, and strengthen the ability to form a thermally stable and condensed barrier for heat and mass transfer. Furthermore, the phosphorus-doped silica-coated polyacrylonitrile fabric provided a novel and efficient method to prepare flame retardant polyacrylonitrile fabric with attractive features.Graphical AbstractIn this article, an efficient and facile method was successfully demonstrated to prepare novel fire retardant PAN fabric. The organic–inorganic hybrid silane coating doped with polyphosphoric acid (PPA) can effectively retard the thermal degradation of PAN fabric, enhane the char-forming ability and can produce a stable and compact shielding layer. The phosphorus-doped silica-coated PAN fabric has lower values of pHRR, THR, pSPR, TSP, aMLR and FIGRA, compared to the control PAN fabric.

Catalytic performance of metal oxide modified SiMCM-41 catalysts in diphenyl carbonate synthesis

Decomposition of CCl4 into diphenyl carbonate (DPC) was examined over metal oxides modified SiMCM-41. ZnO/SiMCM-41 and Fe2O3/SiMCM-41 showed high activity in DPC synthesis. Although many other metal oxides, such as La2O3, CuO, Al2O3 and alkali or alkaline earth oxide, were success in destruction of CCl4, they displayed nearly no activity on DPC synthesis. ZnO/SiMCM-41 and Fe2O3/SiMCM-41 were characterized by X-ray diffraction (XRD), UV-Raman, 29Si MAS NMR and N2 adsorption-desorption isotherms, and results showed that ferric and zinc oxide were supported onto SiMCM-41. The well ZnO dispersion in SiMCM-41 channels and the weak electrostatic interaction between chlorine anion and Zn2+ play an important role for the high activity of ZnO/SiMCM-41 in decomposition of CCl4 into DPC.

Durable flame retardant cellulosic fibers modified with novel, facile and efficient phytic acid-based finishing agent

As a renewable, abundant, and eco-friendly bio-based compound, phytic acid (PA) possesses high phosphorus content, which is a potential flame retardant for cellulosic fibers. Generally, PA is not efficient for cellulosic fibers due to strong acidity that results in greatly reduced strength and lack of soft hand. As proved elsewhere, the compounds with phosphorous and nitrogen was reported to be an efficient flame retardant and exhibited synergistic effect for cellulosic fibers. Therefore, PA was firstly reacted with urea to synthesize a novel green flame retardant containing a high level of phosphorus and nitrogen elements, i.e., phytic acid ammonium, then it was employed for lyocell fibers through pad-dry-cure finishing process. As expected, flame retardancy and durability of finished lyocell fabrics were considerably improved, as evidenced by an increase of limiting oxygen index value up to 39.2% and still 29.7% after 30 laundering cycles. TG–MS and TG–FTIR coupled techniques demonstrate that the formation of carbonaceous residue and non-combustion gases preferably generated during thermal pyrolysis process of finished lyocell fibers.

Preparation of Flame Retardant Polyacrylonitrile Fabric Based on Sol-Gel and Layer-by-Layer Assembly

This paper aims to develop a novel method, i.e., sol-gel combined with layer-by-layer assembly technology, to impart flame retardancy on polyacrylonitrile (PAN) fabrics. Silica-sol was synthesized via the sol-gel process and acted as cationic solution, and phytic acid (PA) was used as the anionic medium. Flame-retardant-treated PAN fabric (FR-PAN) could achieve excellent flame retardancy with 10 bilayer (10BL) coating through layer-by-layer assembly. The structure of the fabrics was characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The thermal stability and flame retardancy were evaluated by thermogravimetric (TG) analysis, cone calorimetry (CC) and limiting oxygen index (LOI). The LOI value of the coated fabric was up to 33.2 vol % and the char residue at 800 °C also increased to 57 wt %. Cone calorimetry tests revealed that, compared to the control fabric, the peak of heat release rate (PHRR) and total heat release (THR) of FR-PAN decreased by 66% and 73%, respectively. These results indicated that sol-gel combined with layer-by-layer assembly technique could impart PAN fabric with satisfactory flame-retardant properties, showing an efficient flame retardant strategy for PAN fabric.

Hydrophilic and antimicrobial properties of acrylic acid and chitosan bigrafted polypropylene melt-blown nonwoven membrane immobilized with silver nanoparticles

The polypropylene melt-blown nonwoven membrane (PPM) is widely used in healthcare; however, the highly hydrophobic nature of the PPM readily adsorbs proteins and polysaccharides, which are conducive to bacteria being retained in the network, resulting in biofouling. Therefore, to improve the hydrophilic and antimicrobial properties of PPM, acrylic acid (AA) was first graft-polymerized on PPM (PPM-g-AA) by ultraviolet (UV)-induced photo-grafting polymerization. Chitosan (CS) was then covalently grafted onto PPM-g-AA to obtain the bigrafted PPM (PPM-g-AA-g-CS). Finally, silver (Ag) nanoparticles were immobilized onto PPM-g-AA-g-CS to create the hydrophilic and antibacterial PPM. The surface chemical composition and morphology of the samples were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. The hydrophilic and antimicrobial properties of the modified PPM were assessed using static water contact angle measurements, wetting time, and bacteria colony-counting assays. The results show that PPM-g-AA-g-CS with immobilized Ag nanoparticles has excellent antibacterial and hydrophilic properties.

Preparation of durable and flame retardant lyocell fibers by a one-pot chemical treatment

Cellulosic fibers are usually finished with flame retardant via repeated pad-dry-cure processes. The present contribution reports a simple, facile, and one-pot chemical treatment process to access durable flame retardant lyocell fibers by directly immersing the fibers into the solution of a flame retardant ester of 2,2-ethanolamine diphosphoric acid (EADP) and urea for a certain time without using catalyst and cross-linker. As demonstrated, the treated lyocell fibers with grafted EADP show excellent flame retardancy and durability, as evidenced by an increase of limiting oxygen index value up to 37.8% and still 25.6% after 40 washing cycles. The key to success is ascribed to the formation of three dimensional flame retardant structures with EADP. Various analytical techniques, including raman spectroscopy, scanning electron microscope, thermogravimetry, and TG-infrared coupled technique prove that the carbonaceous residue and non-combustion gases were preferably generated during thermal decomposition process of treated fibers. Microcombustion calorimetry results revealed a significant reduction in the peak of heat release rate. The results indicate that EADP is potential for using as an efficient durable flame retardant of lyocell fibers.Graphical abstract

4-Benzyl-4-ethyl-morpholin-1-ium hexa-fluoro-phosphate.

The asymmetric unit of the title compound, C13H20NO+·PF6 −, contains two cations, one complete anion and two half hexafluorophosphate anions having crystallographically imposed twofold rotation symmetry. In the cations, the morpholine rings are in a chair conformation. In the crystal, ions are linked by weak C—H⋯F hydrogen bonds into a three-dimensional network.

Fabrication of the SnO 2 /Al 2 O 3 catalysts through electrospinning

SnO2/Al2O3 nanofibers have been fabricated from a suitable inorganic-organic composite solution via a simple electrospinning method and followed by calcination treatment of the electrospun polymer/inorganic composite fibers. The effect of voltage, tip-to-collector distance and calcining temperature on the morphology and crystal structure of nanofibres was investigated by scanning electron microscope (SEM), X-ray photoelectron spectra (XPS) and X-ray diffraction (XRD). The diameter and diameter distribution of nanofibers can be controlled by controlling the electrospinning parameters and the more ideal diameter is 200–350nm. The formation of phase identified by XRD indicated the existence of tetragonal rutile tin oxide crystals and amorphous alumina. This paper provides a new method for the preparation of the SnO2/Al2O3 catalysts for NOX reduction.

The use of electroless plating deposition to prepare Pd/γ-Al 2 O 3 nanofiber catalyst

Gamma-alumina γ-Al<inf>2</inf>O<inf>3</inf>) nanofibres with 30∼ 1500 nm diameter have been prepared by calcination of anhydrous aluminium chloride/polyvinylpyrrolidone (AlCl<inf>3</inf>/PVP) hybrid fibres about 5 h at 900 °C which were prepared by electrospinning as precursor. Nano Palladium (Pd) particles were deposited by electroless plating deposition (EPD) onto γ-Al<inf>2</inf>O<inf>3</inf> nanofibre surfaces to form Pd/γ-Al<inf>2</inf>O<inf>3</inf> nanofibre (PANF) catalyst for the first time. The surface morphology and functional group and elemental concentrations of the Pd/γ-Al<inf>2</inf>O<inf>3</inf> nanofibre Catalyst were examined by SEM, XRD and XPS. The results showed that nano Pd particles round 70∼150 nm in diameter were uniformly distributed on the γ-Al<inf>2</inf>O<inf>3</inf> nanofibre surfaces.