Advanced Materials Research Vol. 911

Abstract: Addition of nanoparticles currently in polymer blends has brought tremendous transformation in polymer engineering field. Incorporation of TiO₂ nanofillers is believed to enhance the physical and mechanical properties of PVC/ENR blends due to its excellent characteristics including non-toxicity, long term stability and UV light discoloration resistance. The main objective of this research work is to introduce titanium dioxide (TiO₂) nanofillers in a range of 0 - 6 phr into polyvinyl chloride (PVC) and epoxidized natural rubber (ENR) blends. Modification on mechanical properties of PVC/ENR blends has successfully been carried via irradiation crosslinking technique. The addition of TiO₂ nanofillers has improved the tensile strength and hardness of the nanocomposites. Nevertheless, at higher loading of 6 phr, the results obviously showed an insignificant difference of performances for both tensile strength and shore hardness properties. Upon radiation of 50 kGy, the increase in Ts of the PVC/ENR blends with addition of 4 phr TiO₂ was found to be optimum before the Ts value drops with higher exposure to irradiation dose rate. Gel fraction of irradiated PVC/ENR/TiO₂ nanocomposites indicates the nanocomposites are crosslinked upon electron beam irradiation. Degree of crosslink was also increased with the addition of 4 phr and 6 phr TiO₂.

Abstract: The reductions of silver nitrate by tannic acid at various pH with and without UV radiation at room temperature were done in order to study the effects of UV radiation and pH of tannic acid solution in the synthesis of silver nanoparticles. The results from UV-Visible spectroscopy, dynamic light scattering method and transmission electron microscopy indicated that using UV radiation resulted in silver nanoparticles with smaller particles and narrower size distribution at every pH. The results also revealed that smallest particles without agglomeration were obtained when alkali condition was applied. Therefore, the suitable condition for synthesizing silver nanoparticles in this research was to use UV radiation and tannic acid solution having pH of 8.0.

Abstract: The effects of processing method and nanofiller size on mechanical performance of biomedical thermoplastic polyurethane (TPU)-organosilicate nanocomposites were examined. High energy milled organofluoromica nanofillers having reduced platelet aspect ratio and tactoid size were produced in order to obtain an overall better dispersion and more efficient TPU-organofluoromica nanocomposite reinforcement. Regardless the processing method, the lower aspect ratio milled nanofillers resulted in improved quality of dispersion and delamination when incorporated into the TPU and hence induced greater mechanical properties as compared to the non-milled nanofiller. However, the high temperature applied in melt compounding process might induce some degree of degradation of the dual surfactants employed, producing free amines and alkenes that can subsequently reduce the molecular weight of the TPU. Therefore, the expected larger increases in mechanical properties of melt blended TPU nanocomposites were not observed.

Abstract: In this study, the photocatalytic degradation of methylene blue has been investigated using natural zeolite modified Mn-doped ZnO nanoparticles synthesized by co-precipitation method. Comparison of degradation efficiency demonstrated that natural zeolite modifiedMn-doped ZnO exhibited higher activity than bare Mn-doped ZnO.

Abstract: Copper doped titanium dioxide (Cu-TiO₂) nanotubes were synthesised by hydrothermal method. The samples were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and nitrogen gas adsorption. The photocatalytic activity of the copper doped titanium dioxide nanotubes was investigated by photodegradation of methyl orange under UV light. The structural and morphological studies showed that, the copper was incorporated into interstitial positions of the TiO₂ lattice to form a new phase of TiO₂ (hexagonal). The copper doped TiO₂ nanotubes possessed high surface area and pore volume, results high photocatalytic activity for degradation of methyl orange (MO).

Abstract: Polymers are excellent host materials for nanoparticles of metals and semiconductors. PVAAgCu nanocomposite was synthesized from chemical reduction, whereas PANIAgCu nanocomposite was synthesized by chemical oxidative polymerization. PVAAgCu and PANIAgCu thin films were deposited on the glass substrate by spin coating technique. The films were characterized by using XRD and AFM. The sensitivity of the samples was analyzed by IV measurement. The peaks in XRD patterns confirm the presence of Ag-Cu nanoparticles in face centered cubic structure. AFM images show the roughness of PVAAgCu and PANIAgCu increased as Ag concentration decreased and Cu concentration increased. I-V measurements indicate that the change in the current of the films increases with the presence of E. coli. The sensitivity on E. coli increases for PVAAgCu and PANIAgCu thin films with high concentration of Cu.

Abstract: Metallic cobalt (Co) nanowires with a mean diameter of about 240 nm and lengths up to 30 μm are grown in solution by electroless deposition under external magnetic. Without magnetic field, only quasi-spherical Co nanoparticles are formed. In the presence of the magnetic field, strong attractive dipolar interactions are induced among the Co nanoparticles. This results in the preferential assembly of Co nanoparticles into nanowires with wire axes parallel to the magnetic field direction. Stronger magnetic field intensity produces longer and thinner Co nanowires. The Co nanowires exhibit ferromagnetic properties at room temperature with an enhanced coercivity of 800 Oe due to shape anisotropy.

Abstract: Strain hardening occurs as a result of extensive plastic deformation of a material at below recrystallization temperature. The powder metallurgy route subjects the elemental powders to highly plastic deformation under compaction; however it is softened while it is sintered. In order to enhance its mechanical behaviour, it is usually subjected to secondary deformation operation. In the present investigation the cold upsetting exercise is carried out in three different lubricants condition with two different preform geometries on sintered Fe-0.75%C. Unlike the conventional material under plastic deformation the matrix gets strain harden, in P/M material along with matrix the geometry supplements the strain hardening behaviour. The nature of matrix and geometric hardening behaviour has been dealt. In addition an empirical relationship and its corresponding parameters experimental values have been predicted which is of high importance in design of preforms and die-set for actual production.

Abstract: It is specified an interrelation between thermal effects in metals phase transformations and changes in structural parameters (coordination number) of the initial and new phases. It is offered the analytical dependences for calculation of the binding energy and atoms coordination numbers, the metals heat of formation, temperature and thermal effects of phase transitions in metals. It is analyzed the energy parameters of the Periodic System elements considering the type of their crystal lattices. By calculation it is estimated structural parameters of liquid and solid phases, thermal effects and the evaporation temperature of crystallization and polymorphic transformation, and energy formation for 55 elements, for which the literature contains reliable experimental data.

Abstract: The phase composition of the AlNiMnFeSiZr system was analyzed with respect to new-generation heat resistant casting aluminum alloys based on a Ni-containing eutectic, which are strengthened by the Al₃Zr (L12) nanoparticles. It is shown that the presence of iron and silicon considerably complicates the phase analysis compared with the AlNiMnFe base alloy. Alloys with low silicon content have a sufficiently good casting property, which enables fabrication of thin-walled castings, not inferior to AA356 alloy types widely used to cast complex shapes. Addition of silicon to the AlNiMnFe base alloy sharply deteriorates hot cracks. Silicon greatly decreases the solubility of Zr at (Al), which is reflected on hot brittleness of Al2%Ni1%Mn0,5%Fe-0,2%Zr system alloys.