Single step preparation of meso-porous and reduced graphene oxide by gamma-ray irradiation in gaseous phase

A facile and highly efficient route to produce simultaneously porous and reduced graphene oxide by gamma ray irradiation in hydrogen is here demonstrated. Narrowly distributed nano-scale pores (average size of ∼3 nm and surface density >44,900 pore μm-2) were generated across 10 μm thick graphene oxide bucky-papers at a total irradiation dose of 500 kGy. The graphene oxide sheet reduction was confirmed to occur homogeneously across the structures by Fourier transform infrared spectroscopy and Raman analysis. This one-step, catalyst-free, high penetration and through-put technique, offers great promises potential for the mass production of reduced graphene oxide from cheap graphene oxide. © 2013 Elsevier Ltd. All rights reserved.

Preparation of pH- and salinity-responsive cellulose copolymer in ionic liquid

A novel biodegradable pH- and salinity-responsive cellulose copolymer was prepared by grafting 2-(Dimethylamino) ethylmethacrylate (DMAEMA) onto bagasse cellulose in ionic liquid. The grafting polymerization was achieved in 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) under microwave irradiation. Copolymers were then characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction and thermo gravimetric analysis measurements. The results revealed that polymer chains had been successfully bonded to the cellulose backbone. Furthermore, the self-assembly of cellulose-g-DMAEMA copolymers at various salt concentrations and pH solution were investigated by means of swelling behavior measurement. It indicated that the copolymers presented dual pH and salinity-responsive properties. The synthetic strategy showed great potential in the modification of other cellulosic biomass to afford new biomaterials with desired properties. © 2014 Springer Science+Business Media Dordrecht.

Preparation of composite electrodes with carbon nanotubes for lithium-ion batteries by low-energy ball milling

Some of the prospective electrode materials for lithium-ion batteries are known to have electronic transport limitations preventing them from being used in the electrodes directly. In many cases, however, these materials may become practical if they are applied in the form of nanocomposites with a carbon component, e.g. via incorporating nanoparticles of the phase of interest into a conducting network of carbon nanotubes. A simple way to prepare oxide-carbon nanotube composites suitable for the electrodes of lithium-ion batteries is presented in this paper. The method is based on low-energy ball milling. An electrochemically active but insulating phase of LiFeTiO4 is used as a test material. It is demonstrated that the LiFeTiO4-carbon nanotube composite is not only capable of having significantly higher capacity (∼105-120 mA h g-1vs. the capacity of ∼65-70 mA h g -1 for the LiFeTiO4 nanoparticles) at a slow current rate but may also operate at reasonably high current rates. © the Partner Organisations 2014.

Preparation of cellulose nanofiber from softwood pulp by ball milling

This paper reports the possibility of producing cellulose nanofiber from softwood pulp using a simple ball milling technique under ambient pressure and at room temperature. The effects of milling conditions including the ball-to-cellulose mass ratio, milling time, ball size and alkaline pretreatment were investigated. It was found that milling-ball size should be carefully selected for producing fibrous morphologies instead of particulates. Milling time and ball-to-cellulose mass ratio were also found important to control the fiber morphology. Alkali pre-treatment helped in weakening hydrogen bonds between cellulose fibrils and removing small particles, but with the risks of damaging the fibrous morphology. In a typical run, cellulose nanofiber with an average diameter of 100 nm was obtained using soft mechanical milling conditions using cerium-doped zirconia balls of 0.4–0.6 mm in diameter within 1.5 h without alkaline pretreatment.

Preparation of size-selective Mn3O4 hexagonal nanoplates with superior electrochemical properties for pseudocapacitors

Porous Mn3O4 hexagonal nanoplates were synthesized through annealing the hydrohausmannite precursor obtained by a one-pot hydrothermal process and by precisely controlling the concentrations of potassium hydroxide and glucose. The effect of potassium hydroxide and glucose on the growth of hexagonal nanoplates was investigated, and a growth mechanism was also proposed. Due to its abundant pores, the pure Mn3O4-based electrode exhibits excellent cycling stability with 100% capacity retention after 5000 cycles. The asymmetric supercapacitor exhibited high performance with an energy density of 17.276 W h kg^-1 at a power density of 207.3 W kg^-1 in a wide potential window of 1.5 V.

Dependence of the electrical conductivity and elastomeric properties on sample preparation of blends of polyaniline and natural rubber

Blend films (free-standing) containing 20% in volume of polyaniline (PANI) in 80% of natural rubber (NR) were fabricated by casting in three different ways: (1) adding PANI-EB (emeraldine base) dissolved in N-methyl-2-pyrrolidone (NMP) to the latex (NRL), (2) adding PANI-EB dissolved in in-cresol to NR dissolved in xylol (NRD), (3) overlaying the surface of a pure NR cast film with a PANI layer grown by in situ polymerization (NRO). All the films were immersed into HCl solution to achieve the primary doping (protonation) of PANI before the characterization. The main goal here was to investigate the elastomeric and electrical conductivity properties for each blend, which may be applied as pressure and deformation sensors in the future. The characterization was carried out by optical microscopy, dc conductivity, vibrational spectroscopy (infrared absorption and Raman scattering), thermogravimetry analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), and tensile stress-strain curves. The results suggest that the NRL blend is the most suitable in terms of mechanical and electrical properties required for applications in pressure and deformation sensors: a gain of conductivity without losing the elastomeric property of the rubber. (c) 2005 Wiley Periodicals, Inc.

Preparation of polymeric micelles for use as carriers of tuberculostatic drugs

Purpose: This paper focuses on the characterization of polymeric micelle-forming tuberculostatic prodrugs and the antimycobacterial activity of these prodrugs.Method: By the condensation of hydroxymethylpyrazinamide, isoniazid and rifampin with free carboxyl groups on the copolymer poly(ethyleneglycol)-poly(aspartic acid), micelle-forming carrier-drug conjugates were obtained. These micelles were characterized by dynamic light scattering, to measure the micelle diameter; by acid-base titration, to determine the percentage of carboxylic groups occupied by the tuberculostatic; by Sudan III solubility tests, to estimate the critical micelle concentration (CMC); and visual control and spectrophotometric measurement, to determine the stability of micelles. These micelles were tested in vitro against several Mycobacterium strains.Results: As expected, the size and distribution of the micelle-forming tuberculostatic prodrugs found to be small (78.2nm, 84.2nm and 98.9 nm) while the level of the drug conjugated was high (65.02-85.7%). Furthermore, the micelles were stable in vitro, exhibiting a low level of CMC and stronger antimycobacterial activity than the original drugs.Conclusion: the results demonstrate that polymeric micelles can be used as efficient carriers for drugs, which alone, exhibit undesired pharmacokinetics, poor solubility, and low stability. The synthesized micelle-forming tuberculostatic prodrugs opens a perspective of alternative prodrugs that prolong action and decrease the toxicity of the tuberculostatic drugs of choice.

Preparation of Ni-Ti-Mo and Ni-Ti-Mo-Zr Alloys by High-Energy Ball Milling and Subsequent Hot Pressing

This work discusses on the preparation of Ni-45Ti-5Mo, Ni-40Ti-10Mo and Ni-46Ti-2Mo-2Zr (at-%) alloys by high-energy ball milling and hot pressing, which are potentially attractive for dental and medical applications. The milling process was performed in stainless steel balls (19mm diameter) and vials (225 mL) using a rotary speed of 300rpm and a ball-to-powder weight ratio of 10:1. Hot pressing under vacuum was performed in a BN-coated graphite crucible at 900 degrees C for 1 h using a load of 20 MPa. The milled and hot-pressed materials were characterized by X-ray diffraction, electron scanning microscopy, and electron dispersive spectrometry. Peaks of B2-NiTi and Ni4Ti3 were identified in XRD patterns of Ni-45Ti-5Mo, Ni-40Ti-10Mo and Ni-46Ti-2Mo-2Zr powders milled for 1h. The NiTi compound dissolved small Mo amounts lower than 4 at%, which were measured by EDS analysis. Moreover, it was identified the existence of an unknown Mo-rich phase in microstructures of the hot-pressed Ni-Ti-Mo alloys.

Preparation of Al2TiO5-Al2O3 and Al2TiO5-Al2O3-TiO2 Ceramics by High-Energy Ball Milling and Sintering

The present work reports on the preparation of Al2O3-TiO2 ceramics by high-energy ball milling and sintering, varying the molar fraction in 1:1 and 3:1. The powder mixtures were processed in a planetary Fritsch P-5 ball mill using silicon nitride balls (10 mm diameter) and vials (225 mL), rotary speed of 250 rpm and a ball-to-powder weight ratio of 5:1. Samples were collected into the vial after different milling times. The milled powders were uniaxially compacted and sintered at 1300 and 1500 degrees C for 4h. The milled and sintered materials were characterized by X-ray diffraction and electron scanning microscopy (SEM). Results indicated that the intensity of Al2O3 and TiO2 peaks were reduced for longer milling times, suggesting that nanosized particles can be achieved. The densification of Al2O3-TiO2 ceramics was higher than 98% over the relative density in samples sintered at 1500 degrees C for 4h, which presented the formation of Al2TiO5.

Preparation of pyrochlore-free PMN by an alternative chemical method

This work reports the synthesis of the MgNb(2)O(6) and the ferroelectric lead magnesium niobate Pb(Mg(1/3)Nb(2/3))O(3) (PMN) using fine precursor powders obtained from a chemical Oxide Precursor Method (OPM). To obtain pyrochlore-free PMN ceramics, the synthesis of the precursor MgNb(2)O(6) powders was studied for 2-25 mol% excess of MgO and 10 mol% excess of PbO. Structural and microstructural properties of the sintered ceramics obtained by the cited method and by the classical columbite method were studied and compared. Results lead to good quality, pyrochlore-free PMN ceramic prepared by OPM, presenting greater grain size if compared with ceramic prepared by columbite method.

Screening of Formulation Variables for the Preparation of Poly(epsilon-caprolactone) Nanocapsules Containing the Local Anesthetic Benzocaine

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of respiratory muscle training on pulmonary function in preoperative preparation of tobacco smokers

OBJETIVO: Avaliar o efeito da utilização de um programa de treinamento específico dos músculos respiratórios sobre a função pulmonar em indivíduos tabagistas. MÉTODOS: Foram estudados 50 indivíduos tabagistas assintomáticos com idade superior a 30 anos, nos seguintes momentos: A0 - avaliação inicial seguida do protocolo de exercícios respiratórios; A1 - reavaliação após 10 minutos da aplicação do protocolo; e A2 -reavaliação final após duas semanas de treinamento utilizando o mesmo protocolo três vezes por semana. A avaliação foi realizada através das medidas de pressões respiratórias máximas (PImax. e PEmax.), picos de fluxo respiratórios (PFI e PFE), ventilação voluntária máxima (VVM), capacidade vital Forçada (CVF) e Volume expiratório forçado no primeiro segundo (VEF1). RESULTADOS: Não houve melhora na CVF e VEF1 da avaliação inicial para a final. Houve aumento significativo das variáveis PFI, PFE, VVM e PImax nas avaliações A1 e A2. A variável PEmax. aumentou somente na avaliação A2. CONCLUSÃO: A aplicação de protocolo de exercícios respiratórios com e sem carga adicional em indivíduos tabagistas produziu melhora imediata na performance dos músculos respiratórios, mas esta melhora foi mais acentuada após duas semanas de exercício.