Applied Mechanics and Materials Vol. 468

Abstract: Colloidal silica modified by sodium aluminate was examined. The particle size of Al-modified colloidal silica was slightly increased with increase of the sodium aluminate concentration, but colloidal silica may aggregate or gel under high concentration. Zeta potential was more negative and thermal stability was significantly improved through modification. The Al-modified colloidal silica was highly stable at pH 3-6.

Abstract: The natural convection of nanofluids in a two-dimensional enclosure is numerically simulated. The effects of nanoparticle concentration and Grashof number (Gr) on heat transfer properties are investigated. The results indicate that for a given initial Gr value, the heat transfer rate of the nanofluid increases remarkably with the increase of nanoparticles mass fraction, and that for low Gr value the heat transfer process is dominant with the heat exchange, while for high Gr value it is dominant with the natural convection. In addition, the intensity of the streamline is increased with the increases of the Gr values.

Abstract: This paper investigated the effects of different pH and dispersant concentration on the dispersion of TiO2 H2O by the measuring zeta potential and absorbency. The results show that the absolute value of zeta potential and the absorbency are higher at pH8-10. Sodium dodecyl sulfate (SDS) can significantly increase the absolute value of zeta potential of particle surfaces by electrostatic repulsions, which leads to the enhancement of the stability for TiO2 nanosuspensions. 0.1%(Mass fraction) TiO2 nanosuspensions has the best dispersion at the SDS optimizing concentration 0.045 %. The results also show the zeta potential has good corresponding relation with absorbency, and the higher absolute value of zeta potential and the absorbency are, the better dispersion and stability in system is.

Abstract: The objective of this work was to investigate the possibility of oilfield produced water (OPW) treatment by moderately compressed exfoliated graphite (CEG) blocks. The CEG blocks were used as filtration materials to treat OPW of Jianghan Oilfield (Qianjiang, Hubei Province, China). The relationship between density and strength as well as the relationship between density and permeable capability of CEG blocks were studied. Furthermore, the maximum OPW treatment ability of CEG blocks was discussed. The main conclusions are as follows: CEG blocks which are used as filtration materials must have both suitable strength and suitable permeable capability. The effect and efficiency of wastewater treatment can be balanced when the CEG density is nearby 0.025 g/cm³. For OPW of Jianghan Oilfield the maximum treatment ability of CEG which has a density of 0.025g/cm³ and a mass of 0.1673g is more than 20L/g if the filtration rate is ignored.

Abstract: The effect of some factors(dosage and grain size of recycled fine aggregate of construction waste, content of mineral admixture) on the properties of cement mortar was studied. The results indicated that when recycled fine aggregate particles gradation was areaⅡ, replacement percentage (sand) was 60%,dosage of mineral admixture was 36%, compared with blank sample, the 28d flexural strength and the compressive strength of cement mortar samples were increased by 30.7% and 37.2%, respectively. Micro-morphology of section on cement mortar was observed by SEM. Identifying the hydration products through XRD was carried out.

Abstract: Mahai salt lake has disadvantages of water shortage and low grade KCl (KCl<8% wt/wt)). First, the brine formula experiment for dissolution slat mine was finished under keeping brine steady seepage, which the KCl content in product brine is greater than 1.2% (wt); then, this work obtained the seepage coefficient that is 1.836×10^-6 m/s; the three-dimensional steady seepage finite element model was build for simulation brine seepage process with different pressure head, and the results showed that the simulation values using the model is basically consistent with the experiment data and the maximum difference is less than 5%. So the model is suit for local dissolution experiment design.

Abstract: A new unsymmetrical photochromic diarylethene with thiazole ring 1-(2,5-dimethyl-3-thiazolyl)-2-[2-methyl-5-(4-hydroxymethylphenyl)-3-thienyperfluorocyclopentene (1o) has been synthesized, and its properties, such as photochromism and fluorescence properties were investigated. Diarylethene 1 changed the color from colorless to orange upon irradiation with 297 nm UV light, in which absorption maxima were observed at 487 nm in hexane.

Abstract: A new unsymmetrical photochromic diarylethene 1o, which is named 1-[2-methyl-5-(4-methoxyphenyl)-3-thienyl]-2-[2-methyl-5-(4-formyphenyl)-3-thienyl] perfluorocyclopentene, was synthesized. Its optical properties, including photochromic reactivity, kinetics and fluorescence properties were investigated in detail. The result indicated that the diarylethene underwent reversible photochromism, changing between colorless and blue in hexane solution and in PMMA, respectively. What is more, the kinetic experiments illustrated that the cyclization/cycloreversion process of this compound was determined to be the zeroth/first reaction. In addition, the results demonstrated that the diarylethene 1o had remarkable fluorescence switching properties.

Abstract: An asymmetrical photochromic diarylethene 1-[2-trifluoromethylpheny-2-[2-methyl-5-(3,5-difluorophenyl)-3-thienyperfluorocyclopentene (1o) was synthesized and its phtochromic, fluorescent properties in both solution and PMMA films were investigated in detail. This compound exhibited remarkable photochromism, upon irradiation with 297 nm UV light, the colorless solution of 1o turned to plum with a new visible absorption band centered at 544 nm (ε =3.75 × 10³ L mol^-1 cm^-1) attributable to the closed-ring isomer 1c.The fluorescence intensity of diarylethene decreased dramatically along with the photochromism from open-ring isomer to closed-ring isomer in PMMA films and in hexane. The emission intensity of diarylethene 1o in a photostationary state was quenched to ca. 64% in hexane and 27% in PMMA films.

Abstract: A novel photochromic diarylethene with a six-membered pyrimidine was synthesized to investigate its photochromic behaviors. This compound exhibited reversible photochromism, changing from colorless to red after irradiation with UV light both in solution and in poly-methyl methacrylate (PMMA) amorphous film. Moreover, it exhibited remarkable fluorescence switching in solution. The results indicated that the pyrimidine moiety played a very important role during the process of photochromic reaction for the diarylethene derivative.