Chong Cui

High-temperature phase transition and the activity of tobermorite

The high-temperature phase transition of tobermorite was investigated by TGA/DSC, X-ray diffraction and Infrared spectroscopy (IR), respectively. The experimental results showed that Si-OH bonds were cleaved at 724 °C and dehydroxylation occured at the same time, implying that the crystal structure of tobermorite was broken. As a result, the dehydroxylation tobermorite was metastable state, exhibiting obviously hydrolysis activity. The suspension was alkaline and Ca2+ ions content reached a maximum value 4.76% after heat treatment at 724 °C. The dehydroxylation tobermorite had potential reactive activity due to the strong hydrolysis activity. The disordered structure recombined to wollastonite, and the crystal structure became ordering and stable at 861 °C Finally, 2M-wollastonite structure can be found in the sample as the temperature reached up to 1 000 °C.

Tribological behavior of MC Nylon6 composites filled with glass fiber and fly ash

To improve tribological property of MC Nylon6, the glass fiber and fly ash reinforced monomer casting nylon composites (GFFAPA) were prepared by anionic polymerization of ɛ-caprolactam. The friction and wear behaviors of composites under dry condition, water lubrication and oil lubrication were investigated through a ring-black wear tester. Worn surfaces were analyzed using a scanning electron microscope. The experimental results show that the tensile strength and hardness of nylon composites are obviously improved with reinforcement increasing. Compared to MC nylon, the lowest friction coefficient and wear rate of glass fiber reinforced nylon composites (GFPA) with GF30% respectively decrease by 33.1% and 65.3%, of fly ash reinforced nylon composites (FAPA) with FA20% decrease by 5.2% and 68.9% and of GFFAPA composites with GF30% and FA10% decrease by 57.8% and 89.9%. The main wear mechanisms of FAPA composites are adhesive and abrasive wear and of GFPA composites with high proportion are abrasive and fatigue wear. The worn surfaces of GFFAPA composites are much multiplex and the optional distributing glass fiber and fly ash have a synergetic effect on the wear resistance for GFFAPA composites. Compared with dry friction, the friction coefficient and wear rate under oil lubricated conditions decrease sharply while the latter reversely increase under water lubricated conditions. The wear mechanisms under water lubricated condition are principally chemical corrosion wear and abrasive wear and they become boundary friction under oil lubricated condition.

Study on Friction and Wear Behavior of Glass Fiber and Fly Ash Reinforced MC Nylon Composites

The glass fiber and fly ash reinforced monomer casting nylon composites (coded as GFFAPA) have been prepared by anionic polymerization of caprolactam. The friction and wear behaviors of composites with different proportion of glass fiber and fly ash under dry condition and water lubrication were investigated through a ring-black wear tester. The worn surfaces were observed and analyzed using a scanning electron microscope and a surface profilometer. The results show that the tribological properties of composites were significantly affected by the proportion of glass fiber and fly ash. GFFAPA composites had lower friction coefficients and better wear resistance than MC nylon. The higher wear resistance of the composite could be attained with the proportion of glass fiber 30% and fly ash 10%, which respectively decreased 57.8% and 89.9%. The main wear mechanism of composites with low proportion of glass fiber and fly ash were adhesive and abrasive wear while that of composites with high proportion of glass fiber and fly ash were abrasive and fatigue wear. Compared with dry friction, the friction coefficient and wear rate of composites Sg3+f1 respectively decreased 42.5% and 77.8% under oil lubricant, while the wear rate was bigger under water lubrication than that with no lubricant. The wear mechanism under water or oil lubricated condition was principally abrasive wear.

Ca(2+) and OH(-) release of ceramsites containing anorthite and gehlenite prepared from waste lime mud.

Lime mud is a kind of solid waste in the papermaking industry, which has been a source of serious environmental pollution. Ceramsites containing anorthite and gehlenite were prepared from lime mud and fly ash through the solid state reaction method at 1050°C. The objective of this study was to explore the efficiency of Ca(2+) and OH(-) release and assess the phosphorus and copper ion removal performance of the ceramsites via batch experiments, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that Ca(2+) and OH(-) were released from the ceramsites due to the dissolution of anorthite, gehlenite and available lime. It is also concluded that gehlenite had stronger capacity for Ca(2+) and OH(-) release compared with anorthite. The Ca(2+) release could be fit well by the Avrami kinetic model. Increases of porosity, dosage and temperature were associated with increases in the concentrations of Ca(2+) and OH(-) released. Under different conditions, the ceramsites could maintain aqueous solutions in alkaline conditions (pH=9.3-10.9) and the release of Ca(2+) was not affected. The removal rates of phosphorus and copper ions were as high as 96.88% and 96.81%, respectively. The final pH values of both phosphorus and copper ions solutions changed slightly. The reuse of lime mud in the form of ceramsites is an effective strategy.

Characterization and Application of New Natural Hydraulic Lime Produced from Lime Mud

AbstractA new natural hydraulic lime (NHL) has been fabricated from lime mud and 5–15% by weight fly ash by calcination and it has been applied to the preparation of fly ash bricks. Lime and dicalcium silicate have been identified as the main crystalline phases of the new NHL by X-ray diffraction (XRD) analysis. Tricalcium aluminate and gehlenite were formed when fly ash content was increased. After calcining at 1,000°C, available lime (31–55% by weight) and sulfate (0.53–0.71% by weight) contents of the new NHL have conformed the performance requirements of NHL. Compressive strength of standard mortars showed that the new NHL met performance requirements. Results also showed that for the new NHL, 900–1,000°C was chosen as the optimum calcination temperature and 10% by weight was the optimum fly ash content. Comparison of the compressive strength of fly ash bricks with the new NHL and ordinary lime has indicated that the new NHL shows better behavior than ordinary lime. Moreover, fly ash bricks with the n...