Key Engineering Materials Vols. 368-372

Abstract: A series of layered-structure Bi-based oxychlorides such as BiOCl, Bi3O4Cl, Na0.5Bi1.5O2Cl, Bi4NbO8Cl and MBiO2Cl (M = Ca, Sr, Ba, Cd, Pb) used as efficient photocatalysts. Among them, Bi3O4Cl (Eg = 2.79 eV), Na0.5Bi1.5O2Cl (Eg = 3.03 eV), Bi4NbO8Cl (Eg = 2.38 eV) and PbBiO2Cl (Eg = 2.45 eV) are visible-light-responsive. The powders synthesized by solid state reactions were characterized by X-ray diffraction (XRD) and UV-Vis diffuse reflection spectrum. Their photocatalytic activities were evaluated by the degradation of methyl orange. The results generally show that the UV-induced photocatalytic performances of the novel oxychloride catalysts are better than or comparable to that of anatase TiO2. The high photocatalytic performance of Bi-based oxychlorides is mainly ascribed to the presence of strong internal static electric fields between layers.

Abstract: In this paper, mass production of quasi-aligned CNTs was achieved with a new tri-metallic catalyst (Fe-Ni-Mo/MgO) by thermal CVD method, using methane as carbon precursor. The growth process was in-situ monitored by thermal gravimetry/differential scanning calorimetry (TG-DSC) technique, and the yield of CNTs over 2200% was attained under the mixture atmosphere of CH4 and H2 with flow rate about 25 ml/min and 5 ml/min respectively at 900°C for 30 min. The as-prepared products were characterized. Raman spectrums showed that the CNTs are multi-wall structure. The diameter of the CNTs was estimated to be 20-30 nm. We think the synergism of FeNi3 alloy and Mo is the main reason for the high catalytic activity of tri-metallic catalyst.

Abstract: The zirconia nanotube arrays on zirconium substrates were formed in (NH4)2SO4 electrolytes containing different concentrations of NH4F (0.5-2.0 wt%). Highly self-organized zirconia nanotubes can be formed with a diameter ranging from 15 nm to 144 nm and a length of 32 μm. The morphology of the nanotubes was strongly influenced by the applied voltages and electrolyte concentrations. Electrochemical testing and scanning electron microscope observation indicated the nanotubes were formed due to the competition of zirconia formation and dissolution under the assistance of electric field.

Abstract: The open-cell macroporous ceramic foams can be used to air and water decontamination after loading catalyst. A new kind of ceramic foam was prepared using pumice, porcelain stone, quartz as main raw materials and polyurethane sponge as template. During the process, the polyurethane sponges were immersed in the powder slurry while submerged to fill all the pores, which makes it uniformly coating the sponge. Then the samples were dried at 80°C, and then sintered at 1050°C -1200°C for 2h in air. The ceramic foams present high porosity from 75% to 90%, higher compassion strength from 10 MPa to 50MPa and lower volume density from 0.15g/cm3 to 0.32g/cm3. The SEM images revealed the open-cell structure in the product.

Abstract: A series of molybdates, Ag2Mo2O7 and AMoO4 (A = Zn, Co), were prepared as a new type of inorganic antibacterial agent via wet chemical routes including hydrothermal synthesis and coprecipitation reaction. The structure and morphology of the samples were characterized with X-ray diffraction and scanning electron microscopy. The anti-bacterial properties of the molybdates against Escherichia coli and staphylococcus aureus were examined, showing good antibacterial behavior.

Abstract: Water-soluble polyethylenimine (PEI) was grafted onto the surface of nano-SiO2 particles through the intermedium effect of 4-bromobutyryl chloride, and the water-insoluble SiO2 containing macromolecular quaternary ammonium salts (MQAS/SiO2) was prepared followed by the N-alkylation of coated PEI with 1-bromohexane and idomethane. The results of FT-IR analysis testified that PEI is successfully immobilized on the surface of SiO2 nanoparticles. The minimum inhibitory concentrations of MQAS/SiO2 against Gram-positive bacterium, Staphylococcus aureus, and Gram-negative bacterium, Escherichia coli, are 100ug/ml and 1200ug/ml, respectively. The bactericidal efficiency of exhaustively washed MQAS/SiO2 did not decline significantly compared to the MQAS/SiO2without washing.

Abstract: In this study, α-ZrP-CPC layered compound was gained by inserting cetyl pyridinium chloride (CPC) into α-ZrP with amines as pillaring agent. The amount of CPC intercalated reached the highest with the molar ratio of the amine/α-ZrP being 2. The lower concentration of CPC resulted in more CPC molecules intercalated into the interlayer of α-ZrP. The intercalation products were characterized by XRD, IR, TG-DSC and SEM. The result of TG-DSC showed that the amount of xylene adsorbed reached the peak value of 5.56%, when the content of CPC in α-ZrP-CPC was 41%.

Abstract: Al2O3-TiO-TiO2 multiphase foam ceramic was prepared with Al powders and TiO2 powders by combustion synthesis, Direct observation and metallographic microscope indicated that the pore diameter is 100~6000μm, and Archimedean method showed that the porosity is 35~50%. The influencing factors of the pore diameter and porosity and, the effects of adding SiO2 on compression strength of the Al2O3- TiO-TiO2 multiphase foam ceramic were discussed. It was shown that the addition of proper high temperature foaming agent can increase porosity and adding SiO2 can decrease porosity. The Al2O3-TiO-TiO2 multiphase foam ceramic has good mechanical properties and high-temperature resistance.

Abstract: With fly ash, metakaolin, slag and alkaline activator as raw materials, the geopolymeric ceramic was synthesized and the properties, such as the weight loss, compressive strength and the structures, at high temperatures of 400~1200°C were measured. The weight loss is in the range of 8~13% from 400°C to 800°C. Comparing with the strength at room temperature, the compressive strength of samples is mostly increased at 400°C and all of them increased at 800°C. 9.65~28.32% strength declines at 1200°C. The variation of the compressive strength with temperature is explained based on the analyses of the phases constitutes and the thermal properties of samples.

Abstract: The phase transformation of Tangshan ironstone-tailings between 900°C ~1200°C in air was investigated by DTA-TG. XRD and SEM analyses indicated that the ironstone-tailings, sintered at 900° and 1000°C respectively, mainly were composed of α-quartz, anorthite [(Na0.45Ca0.55)(Al1.55Si2.45O8)], tremolite and a little of hematite. For the sample sintered at 1100°C, augite appeared and tremolite disappeared. Fayalite formed in the sample sintered at 1200°C. The two samples both exhibited contraction character in the range of experimental temperature.