Advanced Materials Research Vols. 47-50

Abstract: Ternary luminescence coordination compound nanorods composed of rare-earth (Eu(III))- trimesic acid (TMA)-1.10-phenanthroline (phen) were synthesized in alcohol and water mixed solvent. The chemical composition of the obtained sample deduced from the elemental analysis, plasma atomic emission spectra and infrared spectra is Eu (MTA)(phen)·10H2O. Thermal analysis (TG-DTA) showed that the coordination compound has better stability under 463°C, and the decomposition mechanics is Eu (MTA) (phen)·10H2O→Eu (MTA) (phen)·2H2O→Eu (MTA) (C6H6N2)→ Eu2O3. XRD patterns showed that the obtained coordination compound is a new crystal different from that of two ligands. TEM image indicated that coordination compound is nanorods with better dispersity. The diameter of nanorods is about 50~100 nm and the length ranges from hundred nanometer to a few micrometers. Photoluminescence analysis indicated that the coordination compound emits Eu3+ characteristic luminescence under ultraviolet excitation.

Abstract: Manganese is one of metallic elements which appear in biological apatite like bone and teeth. Its important effect on the growth and development of bone has been well known. Here, we have synthesized manganese-doped hydroxyapatite (HA) via sol-gel method. White ammoniacal solution of monomers were refluxed until white gel formed, followed by drying and calcination at 500 – 900°C. Four different concentration of manganese (2, 5, 10 and 15 mol%) were successfully incorporated into HA crystals. XRD analysis showed that the crystallinity increased with the increased amount of manganese. SEM measurement also showed that individual particles become bigger with the increasing content of Mn. Tricalcium phosphate appeared as an additional phase when calcined at 800°C. It was also proven that the incorporation of manganese reduced the peak intensity of tricalcium phosphate. FTIR analysis is in good agreement with the results from XRD measurement where the peaks of OH (630 cm-1) and PO4 3- (565 cm-1, 601 cm-1, 960 cm-1, 1020 cm-1 and 1100 cm-1) bands of HA phase show higher intensity with the increasing concentration of manganese. FTIR measurement also showed that the presence of HPO4 2- (880cm-1) decreased in intensity with the increased Mn content, showing that the anion exist in less crystalline phase of HA.

Abstract: The attention in natural fiber reinforced biopolymer composite materials has been rapidly growing both in terms of industrial applications and basic research. This study was addressed to the investigation of the impact properties and fracture behaviour of biodegradable composites made from egg albumen reinforced by natural cotton fibres. The albumen-cotton composites have been fabricated by hands lay-up technique at varied volume fiber fraction from 2, 4, 6, 8, and 10 vol.% cotton. The specimens were cured at room temperature for a fixed time of 14 days to ensure the specimens are fully dried and harden, before being subjected to mechanical test. The cotton fibres have contributed in a significant improvement in fracture toughness of the composites. The obtained impact strength varied from 15.0 to 19.0 kJ/m2, and the fracture toughness varied from 0.7177 to 0.9453 J depending on vol.% cotton, with the optimum mechanical performance was obtained at 6 vol.% cotton. Morphological observation using SEM revealed that most of the fabricated specimens failed due to fiber breakage, pull out, and void growth.

Abstract: The ethylenediamine trimolybdate (ENTMo) can show unusually photochromic and thermochromic properties and there exists in the difference of chromic mechanisms, which has been proved in our previous work [1]. In this paper, X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) and laser Raman spectroscopy (LRS) of the colored samples are characterized and analyzed in detail. The crystal structure, the inorganic skeleton and the microenvironment of center ions of the colored samples do not substantively change except distortion. The color difference of the photochromic and the thermochromic samples is discussed and that the difference of reduction sites result in their different chromic mechanisms is suggested.

Abstract: The surface-modified Titanium alloy Ti6Al4V was obtained in the process of the double glow discharge plasma hydrogen-free carburizing. The high purity solid graphite as the source cathode supplied the carbon elements; pure titanium and its alloys were used as the cathode and argon as the working gas. At certain pressure and voltage, the glow discharge appeared between cathode and anode, source cathode and anode. The carbon plasma flux, including carbon atoms, ions, sputtered by argon ions diffused into the substrate, which depended on ions bombardment and thermal diffusion at a negative voltage. High purity solid graphite cathode was done in a honeycomb shape or grid shape. A layer with TiC and C phases was formed during the process. Surface hardness was increased by four times due to the presence of TiC and C phases, and wear resistance was enormously improved. The C concentration and hardness of alloying layer changed gradually with the depth. The corrosion properties of hydrogen-free carburized specimens were tested in the solution of 5% NaCl and 5% H2SO4, using electrochemical corrosion method. The results showed that the corrosion resistance of carburized specimens was significantly improved in 5% H2SO4 solution.

Abstract: The influence of nanoclay on the impact damage resistance of carbon fiber-epoxy (CFRP) composites has been investigated using the low-velocity impact and compression after impact tests. The load-energy vs time relations were analyzed to gain insight into the damage behaviors of the materials. Compression-after-impact (CAI) test was performed to measure the residual compressive strength. The CFRPs containing organoclay brought about a significant improvement in impact damage resistance and damage tolerance. The composites containing organoclay exhibited an enhanced energy absorption capability with less damage areas and higher CAI strengths compared to those made from neat epoxy. A 3wt% phr was shown to be an optimal content with the highest damage resistance.

Abstract: The TiO2 nanotubes with a highly ordered structure on titanium were grown by a self-organized electrochemical anodization with viscous organic electrolytes containing small additions of fluorides as the supporting electrolyte. The structure and composition of the as-anodized nanotubes were characterized by field emission scanning electron microscopy. The formation mechanism of the nanotubes was discussed.

Abstract: Mechanical properties of two different types of silkworm silk fibers under three conditions: (i) Bombyx mori; (ii) twisted Bombyx mori; and (iii) Tussah silk fibers were under investigations. The values of ultimate tensile strength, elongation at break and Young’s modulus were examined by performing tensile test on single bave. Scanning electron microscopy (SEM) was used to observe the morphologies of the two different types of silk fibers, and measure their general diameters so as to determine the cross-sectional area of the two different types of silk fibers and convert the experimental load-extension data into stress-strain data accordingly.

Abstract: Due to excellent property enhancement and the versatile application in automotive, aeropspace and ocean engineering applications, research in nanoclay related polymer composites has been a hot topic in the past few years. It is believed that the use of this material to form composites is able to enhance the mechanical, thermal and electrical properties of Polyurethane (PU), Polyester (PE) and Epoxy. However, these composites have only achieved a small strength increment that is below expected potential. For making anti-foulng coatig materials for ocean engineeirng applications, the difficulties are on how to produce uniformly-dispersed nanoclay/polymer composites and avoid clustering effect. In this project, a new experiment setup is proposed to mix nanoclay and epoxy together to form uniformly-dispersed nano-sized nanoclay cluster/epoxy composites. In the experiment, it was found that the micro-hardness of the composites (with 5 wt.% of nanoclay) increased up to 50% under a controlled spinning, curing time and temperature environment.