Advanced Materials Research Vol. 266

Abstract: In this study, the stiffening effect of fillers on asphalt binders was characterized through micromechanics and rheology methods. The dynamic shear rheometer (DSR) was used to measure viscoelastic properties of asphalt mastic. Mechanical volume filling effects and additional interacting mechanisms within mastic systems are discussed on the basis of micromechanics-rheology model to predict the complex shear modulus of asphalt mastic from the measured mastic data. It is observed that the phase angle ranges from 88.8o to 89.0o, does not significantly change due to limestone fillers addition. The analytical model prediction of complex shear modulus based on the dynamic shear modulus can be used. Using the nonlinear regression, the Einstein coefficient KE is 4.22, 5.09 and 7.44 for asphalt mixed with limestone, cement and hydrated lime, respectively. Beside, the SEM results explain why the mastic system with hydrated lime shows the highest KE. The behavior of hydrated lime fillers filled mastics is probably due to physico–chemical interaction, which can be validated by further research.

Abstract: The single-crystalline Fe-doped TiO2 nanowires have been successfully prepared by hydrothermal route. The nanowires have diameter about 50 nm and lengths of several micrometers. The morphological feature and structural characteristics of the samples are studied. Room temperature PL spectra properties and mechanism of Fe-doped TiO2 nanowires in different annealing temperature also are discussed.

Abstract: An optimized synthesis route was applied for controlling the preparation of CdSe quantum dots (QDs) in an aqueous solution. Some key factors which influencing the properties of CdSe QDs, such as initial pH, ratio of precursor etc, were investigated. The as-prepared products have been characterized by TEM, XPS, XRD, UV-Vis and fluorescence (FL) spectra. The result showed that the high-quality CdSe QDs with 3 nm was obtained. The experiments also conformed that the CdSe QDs with better FL properties were obtained with properly initial pH, 5, suitably [Cd2+] / [SeSO3 2-], range from 1:0.25 to 1:0.75 and the ratio of [Cd2+] / [TGA] is 1:2~1:3.

Abstract: A composite photocatalyst of needle nano-ZnO grafted in the pores of expanded graphite (EG) was prepared by a process of hydrolysis method directly, in which the expanded graphite was prepared by microwave irradiation. Scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and Fourier transformation infrared spectroscope (FT-IR) were used to characterize the structure and the chemical structure of the photo-catalyst. The results indicate that expanded graphite had a unique net-like pores structure and needle nano-ZnO was loaded on EG to form EG/ZnO composite photo-catalyst.

Abstract: A composite photo-catalyst of nano-TiO2 (TIO) grafted in the pores of expanded graphite (EG) was prepared by a process that included microwave irradiation method and hydrolysis method directly. Fourier transformation infrared spectroscope (FT-IR), Scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) were used to characterize the structure and the chemical structure of the photo-catalyst. The results indicate that expanded graphite had a unique net-like pores structure and nano TiO2 was loaded on EG to form EG/ TiO2 (EGTIO) composite photo-catalyst.

Abstract: Y2Ce2O7 ceramic material was prepared by solid reaction at 1600°C for 10h. The phase composition, microstructure and thermal conductivity of this material were investigated. XRD results reveals that single phase Y2Ce2O7 with fluorite structure was synthesized. Microstructure of Y2Ce2O7 was dense and no other unreacted oxides or interphase existed in the interfaces between grains. Because of phonon scattering by oxygen vacancies and difference in atomic mass between substitutional atoms and host atoms, thermal conductivty of Y2Ce2O7 is lower than that of 8YSZ, which implies that this ceramic can be used as novel candidate materials for thermal barrier coatings in the future.

Abstract: Coal gangue was used as the main material to fabricate floor tiles in this paper. The mixture of coal gangue, quartz, feldspar and bentonite, with the weight percentage of 55, 20, 20 and 5, was wetly milled, dried, and then pressed into green compacts. The obtained compacts were sintered at 1180-1240 oC and the floor tiles were obtained. The obtained tiles were characterized by XRD, SEM, linear shrinkage, water absorption, bulk density and flexural strength. The results indicate that the tiles were composed of glassy phases, quartz and mullite phases. The phase composition, microstructure, physico-mechanical properties of the samples change with the sintering temperature. The tile sintered at 1220 oC achieves the linear shrinkage, water absorption and bulk density values of 6.18%, 0.16%, 2.45 g/cm3, respectively. Its flexural strength reaches the maximum of 92.0 MPa.

Abstract: Heat treatment is an effective means of structural adjustment and performance improvement of AlN ceramics. AlN ceramics prepared at high pressure with Y2O3 as a sintering aids were heat treated in a nitrogen flow atmosphere. The effects of heat treatment on microstructure and thermal conductivity of AlN ceramics were studied. The results show that the grain size of the AlN ceramics heat-treated at 970 °C for 2 h is significantly increased, the actual crystal morphology is realistic and the second phases are almost present at the grain boundaries or triple pockets compared with the samples without heat treatment, which thermal conductivity has reached 156.7 W/(m·K) from 77.3 W/(m·K). However, the pore size of AlN ceramics is increased and there is the phenomenon of anti-densification while the heat treatment time is extended to 4 h. The thermal conductivity of AlN ceramics heat-treated at 970 °C for 4 h is reduced to 92.6 W/(m·K).

Abstract: In the laboratory condition, a series of experiments were carried out in a sintering pot when Hamersley, Niuman and Hainan lump iron ore were used as sintering hearth layer instead of the recycled sinter. The results show that the sintering productivity is increased by 1.3%, 2.6 % and 13.2 %, and the fuel consumption is decreased by 4.4%, 2.0 % and 6.6 %, respectively. Meanwhile, the tumbler strength and the reduction disintegration index of sinter are also improved. During sintering experiments, the crack of two lump iron ores used as hearth layer didn’t happen. Through using the new technology, the combined water and the sulfur impurity were effectively decreased in the sintering products. Furthermore, the micro-porosity of the sintering products was found to increase, which will contribute to improve the metallurgical properties of sinter.

Abstract: SnO2 nanoparticles were prepared via a sol-gel method by heating the mixture of hydrous SnO2 nanoparticles and SiO2 nanospheres at 600 °C. The average particle size of the obtained SnO2 nanoparticles is 3.3 nm, smaller than that of the SnO2 nanoparticles (~ 6.4 nm) prepared by calcining the pure hydrous SnO2 at 600 °C. The SiO2 nanospheres play an important role in restricting SnO2 nanocrystal growth. The ~3.3 nm-sized SnO2 nanoparticles exhibited high sensitivity for ethanol as well as quick response and recovery time. The concentration detection limit can be as low as 5 ppm at room temperature.