Advanced Materials Research Vols. 383-390

Abstract: A chemical gas sensor for volatile organic compounds (VOCs) detection at trace level is proposed. In this paper, the development and demonstration of the sensor prototype are presented. The prototype is based on a microcantilever resonator that is fabricated from direct bonding silicon-on-insulator (SOI) wafer. The resonant cantilever employs integrated thermal driving and piezoresistive detecting units, and operates in a self-oscillation system. Polyethylenevinylacetate (PEVA) is deposited on top of the cantilever as gas sensitive layer through a spraying method. The responses of the prototype to relative humidity (RH) and six common VOCs: toluene, benzene, ethanol, acetone, hexane and octane have been tested. The PEVA-coated prototype has trace sensitivity to toluene, benzene, hexane and octane, while is insensitive to humidity. The experimental results provide confirmation that the microcantilever resonator is an excellent platform for chemical gas sensor.

Abstract: Growth kinetics of TBAB semiclathrate forming from 32wt% aqueous solution at 10±1°C and atmospheric pressure was studied through macro concentration determination and microscopic observation. The varied concentration from which the hydrate formed was measured in the range of 32wt% ~ 24wt% by means of weighting method, based on which three-stage hydration process was proposed. The morphology of TBAB hydrate crystals and growing velocity were then investigated based on a microscopic observation system. Coexistent morphology of TBAB semiclathrate hydrate crystals was obtained for the first time, with the single crystals in tetragonous, hexagonous, and octagonous columnar shapes. In the kinetics analysis, the growth velocity of TBAB semiclathrate hydrate crystals was calculated. Equation of the crystal growth for tetragonous and octagonous columnar crystals was worked out in combination of the varied concentration and the growth velocity. And to our best knowledge, no kinetics formula has been reported on the two shapes of TBAB semiclathrate hydrate crystals.

Abstract: Prestressed concrete beams with vertically distributed FRP tendons possess some flexural performance obviously different from prestressed concrete beams with steel tendons. This paper provides a complete theoretical approach to analyze and evaluate the flexural behavior of prestressed concrete beams with FRP tendons. Calculation and analysis results show that a prestressed concrete beam with FRP tendons designed at balanced ratio reaches the maximum of its deformability. The increase of prestressing ratio and number of reinforcement layer will increase, respectively, its moment capacity but simultaneously decrease its deformability.

Abstract: Effect of the dosage of flocculants on activated sludge dewatering is analyzed through the determination of sludge specific resistance to filtration．Sludge dewatering behaviors conditioned on PAC, CTS and composite flocculants have been compared. The results show all the conditioning agent have help to sludge dewatering .Compared with Polymeric aluminum , Chitosan(CTS) and PAC/CTS composite coagulant, the optimum coagulant with its optimum dosage is obtained .PAC/CTS can greatly reduce the sludge specific resistance and improves the sludge dewatering performance largely while the clarity of the filtrate was higher.

Abstract: Currently, the number of the waste printed circuit boards (WPCB) is increasing. The technologies of extracting and reclaiming of the value of the metallic fraction of WPCB have been used widely because of the major economic driving force. But the non-metallic fractions (NMFs), which take up almost 70wt% of waste WPCB, were mainly treated by combustion or land filling in the past. However, combustion of the NMFs will cause the formation of highly toxic polybrominated dibenzodioxins and dibenxofurans (PBDD/Fs). Land filling of the NMFs will lead to secondly pollution that caused by heavy meatals and brominated flame retardants (BFRs) leaching to the groundwater. Therefore, recycling of the NMFs from waste PCBs is drawing more and more attention from the public and the governments. How to recycle the NMFs environmental soundly has become a significant topic in recycling of WPCB. This paper briefly introduced that the damage of WPCB and the recycling methods of epoxy resin. The method was established for recycling of WPCB by using solvent extraction. And the optimal conditions were attained through experiments: the reaction temperature was 80°C、the reaction time was 3h、the concentration of nitrate acid was 8 mol/l, the amount of nitrate acid : the quality of WPCB was 50ml/10g.

Abstract: The possibility of using coupling agents for crosslinking composites of wheat straw flour and polyethylene was investigated. The wheat straw flour /polyethylene composites were produced by means of extrusion in order to determine the influence of coupling agent on the mechanical properties of the composites.

Abstract: By the self-made experimental device, the experiment research on the role of relieving differential settlement of subgrade on graded crushed rock in different particle sizes has conducted. The experiment has tested the stress of central, edge and corner of the slab when cavity is produced. The experiment results show that, the graded crushed rock is able to better correspond differential settlement deformation of the subgrade, the liquidity of the bulk particle can fill the cavity spaces. The stress in the slab increases with the addition of the cavity height and the loading. The graded crushed rock with different particles plays different roles on the relief effect of cavity. Generally speaking, the effect of the graded crushed rock in 31.5mm size is better than that of in 19mm size.

Abstract: Based on the research of CFRP reinforced concrete beam , this article indicates that CFRP can improve greatly the fatigue performance of damage concrete beam, prolong its service life , and provide the experimental basis for long-term fatigue properties of CFRP concrete structures.

Abstract: Circular economy promotes the establishment of recycling-oriented society and recycling-based businesses. Circular economy is characterized by eco-efficiency improvement and materials recycle, furthermore, it also has provided a practical and feasible way for the sustainable development of human society. Materials flow analysis (MFA) has provided a new and simple way to study the development of circular economy. MFA is based on materials inputs and outputs, and then creates materials inputs and outputs account to manage materials flow. The process using pyrolusite for FGD produces manganese, high-purified manganese carbonates and slag used for cement production as byproducts. Electrolytic manganese production process, high-sulfur coal combustion process and cement production process are studied in the research. Materials flows of these processes are studied. The new production patterns are compared with the traditional ones basing on MFA. The results show that these processes are more environment-friendly and resource-saving in the comparison. To evaluate the circular economy efficiency of the complementary system, the evaluation index system of the circular economy construction is created.

Abstract: The fine oolitic hematite ore (＜20μm) is easily covered by the ore slime, therefore, it is processed very difficultly with traditional crafts, for example, gravity treatment, magnetic separation, and flotation. The tiny iron ore is unable to recycle effectively, bring about a large of useful minerals running off. It is indicated that the selective flocculation is effective separation craft in many research works. The good dispersion of fine particles is the selective flocculation essential condition, the excessive dispersion will destroy the selective flocculation, at the same time it can be influenced by the water quality, pH, the mixing time, the shear rate and the dispersing agent use level. In this article, to oolitic hematite ore, the chemistry dispersion research is conducted to provide the foundation for further selective flocculation separation.