N.K. Madi

Ion beam modification of surface properties of polyethylene

Abstract Improvement of polymer tribological properties is an essential issue for their application when used as parts of machines or artificial human joints. Ion implantation is a very promising technique in this respect. This paper presents the application of energetic He and Ar ions for this purpose. The materials studied were low-density (LDPE) and high-density (HDPE) polyethylene and their blends. Atomic force and scanning electron microscopes were used for studies of surface modifications. Tribological tests consisted of friction coefficient and nanohardness measurements. Our results have indicated clearly that ion bombardment produces important changes in the polymer surface morphology and its internal structure. The related micromechanical parameters strongly depend on polymer density. For the pristine samples, the friction coefficient increases with decreasing polymer density. For hardness, opposite tendency was observed. A significant increase of hardness and friction coefficient was observed for HDPE subjected to ion bombardment. In contrast, ion bombardment does not produce significant changes of tribological parameters in 50–50 blend and LDPE.

Reduced erbium-doped ceria nanoparticles: one nano-host applicable for simultaneous optical down- and up-conversions

This paper introduces a new synthesis procedure to form erbium-doped ceria nanoparticles (EDC NPs) that can act as an optical medium for both up-conversion and down-conversion in the same time. This synthesis process results qualitatively in a high concentration of Ce3+ ions required to obtain high fluorescence efficiency in the down-conversion process. Simultaneously, the synthesized nanoparticles contain the molecular energy levels of erbium that are required for up-conversion. Therefore, the synthesized EDC NPs can emit visible light when excited with either UV or IR photons. This opens new opportunities for applications where emission of light via both up- and down-conversions from a single nanomaterial is desired such as solar cells and bio-imaging.

Direction of nitrogen migration in iron

Abstract The direction of nitrogen migration has been determined by the analysis of depth distributions of nitrogen implanted into bulk iron and thin iron surface layers.

High performance sulfonic acid doped polyaniline–polystyrene blend ammonia gas sensors

In this work, we present a method of preparation and sensing measurement of four camphorsulfonic acid (CSA) doped polyaniline–polystyrene blends (PANI–PS), where PANI is obtained by dispersion polymerization and blending is conducted by casting method. The effect of CSA concentrations on morphological, optical, thermal and electrical properties has been thoroughly analysed. Interestingly, the morphological analysis (SEM) exhibits different sizes of nanoparticle structures, whereas the FTIR spectra show chemical interaction between the two polymers. DSC data clearly reflects that the blend films carry combined physical properties of both the polymer components. The electrical properties are studied by in-plane I–V characteristics and four probe conductivity measurements. Finally, the blends with high conductivity seem to have good sensitivity and reversibility when used as NH3 sensors.

Improved electrical conductivity of carbon/polyvinyl alcohol electrospun nanofibers

Carbon nanofibers (CNFs) gained much interest in the last few years due to their promising electrical, chemical, and mechanical characteristics. This paper investigates a new nanocomposite composed of carbon nanofibers hosted by PVA and both are integrated in one electrospun nanofibers web. This technique shows a simple and cheap way to offer a host for CNFs using traditional deposition techniques. The results show that electrical conductivity of the formed nanofibers has been improved up to 1.63 × 10-4 S/cm for CNFs of weight 2%. The peak temperature of mass loss through TGA measurements has been reduced by 2.3%. SEM images show the homogeneity of the formed PVA and carbon nanofibers in one web, with stretched CNFs after the electrospinning process. The formed nanocomposite can be used in wide variety of applications including nanoelectronics and gas adsorption.

Retention of nitrogen atoms implanted into carbon

Abstract The retention of nitrogen atoms implanted into carbon was measured by means of Rutherford backscattering spectrometry (RBS). The samples from commercial graphite as well as carbon layers deposited by rf-sputtering in Ar, Ar + N and N plasma were used. The results show that, after room temperature nitrogen ion implantation, the maximum N to C ratio in graphite layers was about 0.25. However, in the deposited carbon layers after nitrogen implantation this ratio reaches 0.54.