High performance hybrid reinforcement of nitrile rubber using short pineapple leaf fiber and carbon black

Rubber composites with very high moduli at low elongation, high elongation at break and high ultimate breaking strength have been developed. The matrix was acrylonitrile butadiene rubber (NBR) and the hybrid (fibrous and particulate) reinforcements were short, fine pineapple leaf fiber (PALF) and carbon black. The amount of PALF was fixed at 10 parts (by weight) per hundred of rubber (phr) while that of carbon black was varied from 0 to 30 phr. Uniaxial NBR composites were prepared. Tensile strength, elongation at break, modulus and tear strength of the hybrid composites were characterized in both longitudinal (parallel to the fiber axis) and transverse (perpendicular to the fiber axis) directions. The addition of carbon black causes the slope of the early part of the stress–strain curve to increase and also extends breaking to greater strains. At carbon black contents of 20 phr and above, the stress–strain relation displays an upturn at high elongations, providing greater ultimate strength. Comparison with the usual carbon black filled rubber shows that the composite behavior at low strains is determined by the PALF, and at high strains by the carbon black. This high performance PALF-carbon black reinforced NBR shows great promise for engineering applications.     

Investigation of the performance of bipolar transverse plate ESP in the sintering flue control

In order to improve the particle collection efficiency of the electrostatic precipitator (ESP), a transverse plate ESP with bipolar discharge electrodes is proposed. The simulations of the velocity distribution have shown that when the inlet velocity is 1 m/s, within the range of 40 mm from electrode plate, the average velocities of windward side and leeward side are less than 0.7 m/s and 0.3 m/s respectively. It is clear that the velocity near the collection electrode plate of this bipolar ESP is much lower than that of the ordinary ESP at the same inlet velocity. This low velocity can lead to higher efficiency for fine dust collection due to the less dust re-entrainment in ESP. It is also found that the average velocities are getting lower when the distance between plates electrodes are greater than 150 mm in accordance with the simulations. The voltage current characteristics of the bipolar ESP are superior to the ordinary ESP. The pressure drop of the bipolar ESP is about 30% higher than that of the ordinary one. The dust penetration of the bipolar ESP is about 54% less than that of the ordinary ESP when the sintering dust with 25.405 μm mass median diameter is used as the test particulate under the condition of the electric field from 2.1 kV/cm to 3.2 kV/cm and the velocity from 1.0 m/s to 1.5 m/s.     

Optical properties of ZnS–carbon nanotubes composites

In this work we present a study of growth and characterization of ZnS/carbon nanotube (CNT) composites. The composites were prepared with a chemical mix technique and characterized by SEM analysis, Auger Electron Spectroscopy (AES) and Cathodoluminescence (CL) spectroscopy. The analyses show that the sample is formed by a direct contact between CNT and zinc sulfide. In particular, SEM images show CNTs wrapped around ZnS micrometer particles. Furthermore, AES spectroscopy shows the absence of chemical bonds between ZnS and CNT and that the sample homogeneity increases with the CNT amount in the composite.Finally CL studies show that our composites present a visible luminescence signal centered at about 500 nm, with a shift of luminescence emission peak linked to the amount of CNT in the sample.     

The fabrication of ReS2 flowers at controlled locations by chemical vapor deposition

Here we report a metal induced nucleation to realize the growth of ReS₂ flowers at controlled locations. The ordered arrays of ReS₂ flowers have been successfully prepared on SiO₂/Si substrate using Pt metal dots as nucleation sites and S, NH₄ReO₄ powders as precursors by a chemical vapor depostion method. The NH₄ReO₄ powders are used as the rhenium sources. The ReS₂ flowers are grown above the pre-patterned Pt dots, Raman and transmission electron microscopy measurements indicated that the prepared ReS₂ flowers have excellent crystalline quality.     

Sulfonated reduced graphene oxide as a highly efficient catalyst for direct amidation of carboxylic acids with amines using ultrasonic irradiation

Sulfonated reduced graphene oxide nanosheets (rGO-SO₃H) were prepared by grafting sulfonic acid-containing aryl radicals onto chemically reduced graphene oxide (rGO) under sonochemical conditions. rGO-SO₃H catalyst was characterized by Fourier-transform infrared (FT-IR) spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and X-ray photoelectron spectroscopy (XPS). rGO-SO₃H catalyst was successfully applied as a reusable solid acid catalyst for the direct amidation of carboxylic acids with amines into the corresponding amides under ultrasonic irradiation. The direct sonochemical amidation of carboxylic acid takes place under mild conditions affording in good to high yields (56–95%) the corresponding amides in short reaction times.     

Ion-exchange between Na2Ti3O7 and H2Ti3O7 nanosheets at different pH levels: An experimental and first-principles study

The models of Na_2−xH_xTi₃O₇ (x=0, 1, and 2) nanosheets were proposed to investigate the formation energies of ion-exchange using first-principles calculations. The calculated results demonstrated that sodium titanate nanosheet is energetically favorable for ion-exchange in a wide pH range, from acidic solution to even highly concentrated alkaline aqueous solution due to the negative formation energies. Therefore, the composition of sodium titanate nanosheet in alkaline solution should be Na_2−xH_xTi₃O₇ (0<x≤2) rather than Na₂Ti₃O₇. The formation energies of ion-exchange decrease with the pH decreasing. As a result, the thermodynamic driving force of ion-exchange is enhanced at low pH level. To further verify the calculated results, the ion-exchange properties of a series of titanate nanosheets in aqueous solutions at different pH levels were investigated. The experimental results are in good agreement with the theoretical deduction.     

Predicting vibration-induced displacement for a resonant friction slider

A mathematical model is set up to quantify vibration-induced motions of a slider, sandwiched between friction layers with different coefficients of friction, and equipped with an imbedded resonator that oscillates at high frequency and small amplitude. This model is highly nonlinear, involving non-smooth functions with strong harmonic excitation terms. The method of averaging is extended to hold for systems of this class, and used to derive approximate expressions for predicting average velocities of the slider. These expressions are shown to produce results that agree very well with numerical integration of the full equations of motion. The expressions are used to estimate and explain the influence of system parameters.     

Towards the synthesis of insulated oligoynes: A ring-closing-metathesis approach to molecular encapsulation

Masked hexayne 18 was prepared in 11 steps from commercially available reagents. The four butenyl substituents contained within the two arylsilane residues in 18 have been used in a double ring-closing-metathesis operation in an attempt to encapsulate the π-conjugated framework. When 18 was treated with Grubbs’ 1st generation metathesis catalyst however, double ring-closing metathesis provided macrocycle 19 as the major product in good yield. Reasons why the macrocycle in 19 crowns, rather than encapsulates, the π-conjugated framework are discussed.     

X-ray photoelectron spectroscopy of LiM0.05Mn1.95O4 (M = Ni,Fe and Ti)

LiMn₂O₄ and LiM_0.05Mn_1.95O₄ (M = Ni, Fe and Ti) were synthesized by using solid-state reactions and their surface stoichiometries were confirmed by XPS data. The crystal and electronic structures were investigated by using X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). XRD data suggested that LiM_0.05Mn_1.95O₄ possesses nearly no any variations in lattice parameters compared with LiMn₂O₄ for slight substitution of Ni, Fe and Ti; the substituted Ni, Fe and Ti ions were located on the 16d octahedral sites in the spinel crystal lattice. The XPS results suggested that Fe and Ti ions were at + 3 and + 4 oxidation states, respectively; while Ni ions are mixed with + 2 and + 3 oxidation states. The normal oxidation state of Mn ions in the above four materials is almost the same and calculated as + 3.55 according to the splitting energies of Mn3s states.