No abstract

Silver/polyaniline nanocomposites (Ag NPs/PANI) containing PANI nanofiber and Ag nanoparticles were synthesized by one-step approach without using any extra reducing agent or surfactant and applied to new antimicrobial agents. Morphologies and crystallinity of the nanocomposites were characterized with SEM and XRD. The results showed that the average diameter of the PANI nanofibers is around 50-150 nm, and the average particle size of Ag NPs is around 100 nm. The crystallinity of PANI gets better with increasing silver nitride concentration. UV-vis absorption spectroscopy analysis indicated that the Ag NPs have some effect on the microstructure of PANI. The antimicrobial properties of Ag NPs/PANI against Gram-negative Escherichia coli, Gram-positive Staphylococcus aureus and fungous Yeast were evaluated using viable cell counts. The test results demonstrated that Ag NPs/PANI have enhanced antimicrobial efficacy compared to that of pure Ag NPs or pure PANI under the same test condition. The mechanism of the synergistic antimicrobial effect of Ag NPs with PANI was also proposed. In addition, thermal gravity analysis indicated that pure PANI and Ag NPs/PANI exhibit better thermal stability.

Li 4 SiO 4 -based sorbents from diatomite with fast CO 2 adsorption rate (achieving the adsorption equilibrium at about 15 min) were developed by the impregnation precipitation method at lower temperature (600 °C). Influence of sintering temperatures on phase composition was investigated. Phase composition and morphologies were analyzed by XRD and SEM, and CO 2 adsorption properties were investigated by TG. The as-prepared Li 4 SiO 4 -based sorbents reached a higher adsorption capacity of 34.02 wt % (7.73 mmol CO 2 /g Li 4 SiO 4 , corresponding to 92.70% efficiency) in a mixture gas (50 mL/min N 2 and 50 mL/min CO 2 ). The activation energies for chemisorption (28.868 kJ/mol) and diffusion (16.563 kJ/mol) were obtained by isothermal study. Compared with our previous research results by the solid reaction method, the activation energies for these two processes decreased measurably. In addition, the as-prepared Li 4 SiO 4 -based sorbents also exhibited faster adsorption rate and better adsorption−desorption performance.

No abstract

Porous silicon nitride (Si3N4) ceramics with about 50% porosity were fabricated by pressureless sintering of α‐Si3N4 powder with 5 wt% sintering additive. Four types of sintering aids were chosen to study their effect on the microstructure and mechanical properties of porous Si3N4 ceramics. XRD analysis proved the complete formation of a single β‐Si3N4 phase. Microstructural evolution and mechanical properties were dependent mostly on the type of sintering additive. SEM analysis revealed the resultant porous Si3N4 ceramics as having high aspect ratio, a rod‐like microstructure, and a uniform pore structure. The sintered sample with Lu2O3 sintering additive, having a porosity of about 50%, showed a high flexural strength of 188 MPa, a high fracture toughness of 3.1 MPa·m1/2, due to fine β‐Si3N4 grains, and some large elongated grains.