Advanced Materials Research Vol. 650

Abstract: Multiwalled carbon nanotube/electroactive polyurea (MWCNT/EPU) composites have been synthesized through oxidative coupling polymerization. The amino functional groups on AF-MWCNTs provided an opportunity to react with oligoaniline in oxidative coupling polymerization process. UV-visible spectra reveals that the quinoid ring on the EPU interact with MWCNTs. The results of the cyclic voltammetry studies indicate enhanced electrochemical properties for efficient electron/charge transfers behavior of MWCNT/EPU composites.

Abstract: In this study, mesoporous silica nanoparticles were synthesized through sol-gel method, employing tetraethylorthosilicate (TEOS) as a precursor under base-catalyzed condition. The reaction temperature was kept constant at 50→C. The results indicated that the properties of silica nanoparticles could be controlled by altering the calcination temperatures. It has been found that silica nanoparticles synthesized under base-catalyzed and calcined at 600→C are uniform, well-dispersed and spherical-shaped. The anti-reflective behavior and the methylene blue adsorption capacity are optimized when calcined at this temperature.

Abstract: Porous carbons were synthesized from commercial sugar via microporous silica template method in order to control the micropore structure of carbon. The silica template used in this study had a uniform particle size, a specific surface area of 991 m²/g and an average pore size of 2 nm. The effects of carbonization temperature and the content of silica template were investigated. The results showed that the carbonization temperature of 800→C and 50%SiO₂/C yielded the maximum methylene blue and iodine adsorption capacity. However, due to microporous nature, a partial dissolution of the silica template with HF solution occurred and blocked the pore entrance, reducing the adsorption capacity and specific surface area of carbon. The specific surface area as high as 1,134 m²/g was, therefore, achieved with porous carbons synthesized without nanoporous silica template.

Abstract: Mixing is the first step for rubber processing. For the short fiber-rubber composite materials, whether the short fibers, carbon black and other additives in the rubber are dispersed well or not has a direct bearing upon the subsequent processing of materials and final performance. Because of the softness of the short fibers, they are easy to group or break during the process of mixing. The research in this paper is conducted by experiment on the methods which are applicable for mixing or mixing rotor of short fiber-rubber composite materials so as to guarantee the materials have good dispersion and the short fibers have rational L/D ratio.

Abstract: Due to their significant impacts on the environment and health, there has been a growing environmental concern on sulfur oxide (SO_x), nitrogen oxides (NO_x) emissions to the atmosphere in the past two decades. Flue gas at coal-fired power stations is one of the main sources for the emissions of SO_x and NO_x. More and more stringent regulations on the emission of these pollutants come in force, which have put a high pressure on coal-fired power generators. Cost-effective and sustainable technologies for the reduction of such pollutants from flue gas have become increasingly important nowadays. However, even though numerous attempts have been made aiming at developing technologies for the removal of SO_x and NO_x, not much effort has been made on the simultaneous conversion of NO_x and SO_x in flue gas via selective catalytic reduction. This paper presents the study of simultaneous removal of SO₂ and NO over a synthesized Cu/Na-13X zeolite catalyst using carbon monoxide as a reducing agent. The characterization of fresh and spent catalysts was carried out using X-Ray Diffraction (XRD) and Brunauer-Emmett-Teller (BET) Surface Area Analyser. The experiments on the selective reduction of SO₂ and NO were carried out using a multi-functional catalyst testing rig with an online flue gas analyser. It has been found that zeolite has a good capability of SO₂ adsorption even under elevated temperatures. The removal efficiency was found to be 100% for SO₂ and 89% for NO over a Cu/Na-13X zeolite catalyst.

Abstract: The protecting of concrete, which consists of coating a chemical substance onto concrete’s surface, has been applied to architectural conservation. There is increasing interest in studying materials for concrete which can reduce the infiltration of water and salt solutions and rehabilitate and extend its service life. Silicon compounds are frequently used as a base for commercial protecting paint due to their hydrophobicity and penetrability. However, the stability of the impregnant emulsion is affected by many factors. The effect of three main factors such as component, pH, and emulsifier were studied in this paper. The stability of the impregnant decreased with the increase of pH. And the mixed emulsifier and 4～6% amount of emulsifier would be optical for the stability of the system and maintain the activity at the same time.

Abstract: The effects due to fluid pH and dispersant concentration on the dynamic viscosity for the Al₂O₃–water and TiO₂–water nanofluids had been experimentally investigated. The viscosity of the two kinds of nanofluids was measured using capillary viscometers. The experimental results showed that there exists an optimized value of pH (pH≈8.0) at which the viscosities of the two nanofluids take their minima values. The experimental results also showed that the influence of dispersant concentration on the viscosity of Al₂O₃–water suspension was relatively large comparing with that of the TiO₂–water nanofluid, and the dispersion of alumina powder is poorer than that of titanium dioxide powder at the same pH value and same mass fraction.

Abstract: Along with the development of high speed machining technology, the ball end milling cutter’s application is more and more widely. An influence of four control parameters, namely feed, cutting depth, spindle speed and cutting width, on cutting forces is investigated. This paper focuses on experimental research of milling process of carbon fiber reinforced carbon matrix composite (C/C composite). The milling force prediction model for milling of composite using the carbide ball-end tools is built by orthogonal experiment. The experiment results show that : the reliability of the this prediction model is quite high, and the effect of milling speed on milling force is not very obvious, but the milling force increases with the increment of feed per tooth, milling depth and milling width. Using this information, a new prediction model for the milling forces is proposed that can be used for C/C composite milling.

Abstract: The synthesis of a silicon thin film by room-temperature electrodeposition was investigated in the ionic liquids 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide ([EMIM]Tf₂N) and 1-butyl-3-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMPy]Tf₂N) with SiCl₄. Cyclic voltammetry on a gold working electrode showed the possibility of the electrodeposition of elemental silicon. The reduction current of silicon in [EMIM]Tf₂N was higher than in [BMPy]Tf₂N. The elemental silicon thin film could be synthesized on the gold electrode under potentiostatic conditions, as confirmed by various analytical techniques including X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy with energy-dispersive spectroscopy. In the [EMIM]Tf₂N electrolyte with dissolved SiCl₄, the electrodeposited Si surface was more uniform than in [BMPy]Tf₂N and no impurity was detected except trace oxygen caused by contamination during handling for analysis

Abstract: The silanol groups on Silica gel surface are sites for adsorption of polar molecules. Alcohols and other polar molecules are easily adsorbed by forming hydrogen bondings with OH groups on silica gel surface. A study on the adsorption of methanol on silica gel was carried out by using NIR spectroscopy in combination with ssecond derivative techniques. Four of the well characterised silica gel samples were used in this study. Each of the silica gel (0.25g) samples with different surface areas and silanol number was pressed into a small disc, placed in a glass vial and the physically adsorbed water molecules from the surface of the silica gel particles were removed by heating the sample to 200 °C under vacuum. The near infrared spectra of the cooled sample was recorded by a Perkin Elmer spectrum one NIR spectrometer equipped with a transflectance accessory and a deuterated triglycine detector at a resolution of 16 cm-1. The glass vial was then opened and a tiny tube filled with methanol was inserted in the glass vial. Then the near infrared spectra of the sample during the adsorption of methanol were recorded at regular time intervals until there is no apparent change in the spectra. The second derivative profiles of the spectra were obtained using the instruments’ software. The mass of the silica gel pellet was determined by an analytical balance and the methanol adsorbed on the surface was calculated. The number of methanol layers on the silica gel surface was calculated using the silica gel particle characteristics of the samples. The results show that the adsorption evolution of methanol progresses on the samples and the surface was covered by a mono layer within the first 60 minutes. Furthermore, it appears that the adsorption of multilayer on methanol starts after all the surface silanol groups are exhausted.