Advanced Materials Research Vols. 150-151

Abstract: The influence of curing time on the mechanical property of the phosphoaluminate cement (PAC) was investigated, and the mechanism was discussed as well. The phase composition and morphology of hydration products, electrical properties, porosity and pore size distribution of PAC cured different age were analyzed with XRD, EIS and MIP. The results showed PAC has the property of early-high strength, and the compressive strength of PAC cured for 1 day was about 70% of 28 days’. The main hydration products of PAC are micro-crystal phase and gel of phosphate and phosphoaluminate which formed compacter microstructure. In addition, there are no calcium hydroxide (CH) and ettringite (AFt) produced during the process of hydration. The compressive strength of PAC increased with age, which was due to more products continuously produced. The ac resistance analysis manifested as the change of the nyquist pattern and resistance value.

Abstract: The influence of curing time on the mechanical property of the phosphoaluminate cement (PAC) was investigated, and the mechanism was discussed as well. The phase composition and morphology of hydration products, electrical properties, porosity and pore size distribution of PAC cured different age were analyzed with XRD, EIS and MIP. The results showed PAC has the property of early-high strength, and the compressive strength of PAC cured for 1 day was about 70% of 28 days’. The main hydration products of PAC are micro-crystal phase and gel of phosphate and phosphoaluminate which formed compacter microstructure. In addition, there are no calcium hydroxide (CH) and ettringite (AFt) produced during the process of hydration. The compressive strength of PAC increased with age, which was due to more products continuously produced. The ac resistance analysis manifested as the change of the nyquist pattern and resistance value.

Abstract: The alicyclic dianhydrides 1,2,3,4-cyclobutanetetracarboxylic dianhydride(CBDA) was polymerized with four kinds of fluorinated aromatic diamine, 2,2’-bis(trifluoromethyl)-4,4’- diaminobiphenyl(TFDB), 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene(6FAPB), 1,4-bis(4- amino-2-trifluoromethylphenoxy) diphenyl ether (6FAPE) and 1,4-bis(4-amino-2-trifluoromethyl- phenoxy)diphenyl(6FBAB) respectively, via a two-step polycondensation procedure to prepare four series of fluorinated polyimides(PIs) derived from CBDA. The obtained PIs displayed excellent solubility in aprotic polar solvents, such as NMP, DMAc, DMF and DMSO. These PIs showed good thermal stability with the 10% thermal decomposing temperatures higher than 457 in nitrogen and the glass transition temperatures higher than 267 . In addition, the PI films exhibited good optical transparency in the visible light region(400-700nm) with the transmittance higher than 80% at 450nm, and the PI films showed little absorption at the optocommunication wavelengths of 1.30µm and 1.55µm.

Abstract: A weak acid cation exchange fiber was prepared by γ-ray pre-radiation induced grafting of acrylic acid (AA) onto polypropylene (PP) non-woven without removal of the polymerization inhibitor in acrylic acid. The factors influenced the grafting degree were discussed, such as radiation dose, initiator concentration, monomer concentration, storage time and bath ratio. It is found that the initiator 2, 2'-Azobisisobutyronitrile (AIBN) was necessary for the increased grafting of AA without removing the inhibitor in AA.

Abstract: In this work, the effect of stirring time on the solidifed microstructures and mechanical properties of semi-solid Sn-Bi slurry was investigated by the mechanical stirring method. The results indicated that a fine round granular solidifed structure of Sn-Bi semi-solid slurry was obtained at 142 and stirred for 8 min. Compared with the Sn-Bi alloy prepared conventional die casting, the mechamical properties of semi-solid Sn-Bi alloy was improved prominently. The percentage elongation of semi-solid Sn-Bi alloy was increased 67 % compared with that of the Sn-Bi alloy prepared conventional die casting.

Abstract: The principle, of which the ZnSe thin films are co-deposited in the ZnSO4 and Na2SeO3 acidic solution by electrochemistry, is explained by the electrode-solution interface action model. The current density and the duty cycle of the pulse current promote the diffusion of solution and affect the co-deposition of the ZnSe films. The ZnSe thin films are pulse electrodeposited in zinc sulfate, selenite sodium and sodium citrate acidic solution. The sodium citrate, which is one kind of complex agent, simultaneous also one kind of buffer agent and has certain buffer action, would affect the quality of the ZnSe films. Finally, the ZnSe films have been characterized by the scanning electron microscope (SEM) and the energy dispersion analysis of X-ray (EDAX).

Abstract: Based on nonlinear finite element method, the influence of tunnel construction on adjacent underground pipeline is studied. It is shown that remarkable settlements occurred above tunnel working surface due to tunnel excavation, and soil bulged below tunnel working surface due to load-off. The inhomogeneous deformation of pipeline become more serious when the distance between tunnel working surface and pipeline become shorter. So it is important to keep enough distance between tunnel working surface and pipeline. The deformation of pipeline become less when the radius of tunnel decreased. It is also find that there is no obvious influence on settlement of pipeline with different materials of pipeline. The settlement of pipeline can be reduced and stability of tunnel can be enhanced evidently by local excavation above tunnel working surface. Therefore, local excavation above tunnel working surface can be prior used to protect underground pipeline if allowable.

Abstract: Fused quartz granule (d50=0.033mm) was used as raw material, Pr6O11, Sm2O3, Gd2O3, Dy2O3 and Ho2O3 were used as additives with dosage of 2% each. Fused quartz ceramic materials were fabricated in reduction atmosphere at 1300°C, 1400°C and 1500°C for 1h. Samples were examined apparent porosity, bending strength, thermal expansion rate (RT~1200°C), and analyzed by XRD and SEM. The results indicated that additives Pr6O11, Sm2O3 and Dy2O3 had a bit inhibiting effect on crystallization of fused quartz sintered at 1300°C and 1400°C, Ho2O3 and Gd2O3 had more inhibiting effect on crystallization in samples sintered at various temperatures, sample containing Ho2O3 had least thermal expansion rate. Pr6O11, Sm2O3 and Dy2O3 had few facilitating effect on sintering, Gd2O3 and Ho2O3 had more facilitating effect on sintering of fused quartz ceramic materials, samples with Gd2O3 and Ho2O3 had lower apparent porosity and higher bending strength and more compact microstructure. It can be deduced that Gd2O3 and Ho2O3 play the excellent role as the crystallization inhibitor to fused quartz materials.

Abstract: Fused quartz ceramic was prepared in air atmosphere at 1300°C, 1350°C and 1400°C for 1h with fused quartz powder as raw materials (size<0.06mm) and with nano-Cu2O or nano-ZrO2 as additives (size<0.1μm). The effect of nano-Cu2O and nano-ZrO2 (size<0.1μm) on crystallization and sintering of the fused quartz ceramic materials were researched by measurements of apparent porosity, bending strength and thermal expansion rate, and analyses of XRD and SEM. The results showed that nano-Cu2O had detrimental effect on sintering and promoted crystallization of fused quartz, and nano-ZrO2 had better facilitating effect on sintering and better effect of inhibiting crystallization of fused quartz. So, samples with nano-ZrO2 had lower apparent porosity and higher bending strength and more compact microstructure and least thermal expansion rate.

Abstract: This paper investigated the influence of activator concentration, reaction time and fineness of fly ash on the dissolving character of the active Si/Al in fly ash activated by alkali. The results indicated that with the increase of the NaOH solution concentration, the dissolving percentage of active Si/Al in the fly ash went up. The finer the fly ash particles were, the higher dissolving percentage of active Si/Al was obtained. Under strong basic (2M NaOH solution) and boiling condition, the reaction time of active Si/Al dissolving was short and less than 10 minutes. The content of vitreous phase contributed to the content of active components. Active Si existed in the state of Q0 unit which presented an isolated silicon-oxide tetrahedron in fly ash, and active Al exhibited as Al[OSi]3 and Al[OSi]4 units in 4 coordinate. As the fly ash was activated by alkali, smooth shell of fly ash was gradually corroded by NaOH solution, glass phase was dissolved and crystal phase was exposed to the outside.