Advanced Materials Research Vol. 410

Abstract: Among different sterilization methods, heat-treatment of bone is recognized as one of the simple and practical methods to lower the human immunodeficiency virus (HIV) infection and overcome the risks of rejection and disease transfer from allograft and xenograft during bone transplantation. In order to best characterize the micro-structural mechanical property of bone after heat treatment, the nanoindentation technique was applied in this study to measure the localized elastic modulus and hardness for interstitial lamellae and osteons lamellae of bovine cortical bones at temperature 23°C (room temperature-pristine specimen), 37°C, 90°C, 120°C and 160°C, respectively. The elastic modulus (E) and hardness (H) of interstitial lamellae obtained higher values as compared with osteons lamellae which show that interstitial lamellae are more stiff and mineralized than osteons. Moreover, as a specimen pre-heat treated at 90°C, the E and H values of interstitial lamellae and osteons were closed to a pristine specimen. For a specimen pre-heat treated at 120°C, both interstitial lamellae and osteons obtained an increase in E and H values. As a specimen pre-heat treated at 160°C, the interstitial lamellae and osteons obtained a slight decrease in E and H values. These findings are correlated to results reported by other researchers [1, 2] that calcified collagen molecules starts to degenerate at about 120°C and complete at 160°C. Interestingly, when a specimen was pre-heat treated at 37°C, both interstitial lamellae and osteons obtained significant decreases in E values of 57% and 40%, respectively as compared to the pristine specimen; while in H values, there was a decrease of 27.4% and 15%, respectively. Thus, this paper will investigate the mechanical properties of bovine cortical bones under various temperature ranges by nanoindentation technique.

Abstract: In the current age of growing environmental awareness, natural fibre composites have gained wide acceptance in various facets of engineering. However, in industries, such as aerospace and mining, their acceptance is primarily dependent on them meeting the stringent fire test requirements. In this paper, symmetric laminates consisting of only glass, glass/flax hybrid and only flax as reinforcements in thermoset matrices were tested for their time to ignition, heat release rate and smoke constituents as per standard ASTM E 1354 in a cone calorimeter. Four fire retardant versions of resin systems, were used in this study. The laminates were manufactured using wet hand-layup technique that was vacuum bagged and cured between hot platens of a hydraulic press. A constant fibre volume fraction of 0.5 for all the laminates was obtained by maintaining a constant laminate thickness of 4mm. The results from the cone calorimeter tests were compared to examine the influence of natural fibres on the fire properties of the laminates. It was observed that the degree of fire retardance in the polyester based composites decreased with the increase in the flax fibre content; however, in the modified urethane composites, flax fibre composites performed better by exhibiting higher ignition time compared to the hybrid and glass fibre composites. Another important observation was that the carbon monoxide emissions during testing decreased with the increase in flax content in the composites, no matter what resin system was used. These preliminary tests suggest that, by judiciously incorporating natural fibres in a synthetic system, a hybrid system could be designed to sustain loads in environments with high fire risks.

Abstract: Over the past decade, intensive research has been conducted on electrospinning of fibrous tissue engineering scaffolds and their applications in body tissue regeneration. For providing multifunctions and/or enhancing the biological performance, drugs or biomolecules can be incorporated in electrospun fibers using normally one of these techniques: (1) direct dissolution, (3) emulsion electrospinning, and (3) coaxial electrospinning. In this investigation, for constructing nanofibrous delivery vehicles, conventional electrospinning using polymer solutions with directly dissolved drugs or biomolecules and emulsion electrospinning were studied and compared. Bovine serum albumin (BSA) was used as a model protein and the drug was rifamycin, a hydrophobic antibiotic. A poly (lactic-co-glycolic acid) containing the protein or drug was electrospun into fibers. In these two routes of fabricating drug-or biomolecule-loaded nanofibers, different polymer concentrations and emulsion formulations were investigated. Various aspects of the fibrous delivery vehicles were investigated using several techniques and the in vitro release behaviour was studied.

Abstract: In this study, Jute fibers reinforced polypropylene (JFRP) composites were manufactured by injection molding technique. Prior to fabrication of composites, fiber surface was treated by Alkali and Plasma for a rise in fibers properties. Furthermore, after the alkali treatment attempt plasma treatment for the fiber surface treatment to obtain a batter value. In order to improve the affinity and adhesion between fibers and thermoplastic matrices during manufacturing, Maleic anhydride (MA) as a coupling agent have been employed. Untreated and treated surfaces of jute fibers were characterized using SEM. Tensile and flexural tests were carried out to evaluate the composite mechanical properties. Tensile test indicated that 3% of the alkali treatment and 2min plasma treatment fiber has highest tensile strength.

Abstract: N-(2-Amino-phenyl)-2-{2-[(2-amino-phenylcarbamoyl)-methoxy]-phenoxy}-acetamide (B) was firstly immobilized on the single-walled carbon nanotubes and characterized by ¹H NMR, IR spectra and TEM images. The longer ⁵D₀ fluorescence lifetime was observed in the europium (III) complex of this functionalized carbon nanotube than in the Eu (III) complex of free B.

Abstract: Carbon nanotube (CNT) reinforced magnesium alloy (AZ31)-based composite was fabricated using the technique of solidification processing followed by hot extrusion. In this paper is presented and briefly discussed the conjoint influence of reinforcement and processing on microstructural development, microhardness, tensile deformation and final fracture behavior of the magnesium alloy composite and comparisons made with the unreinforced alloy (AZ31). The interactive influences of the CNT reinforcement and processing in governing engineering stress versus engineering strain response and tensile properties is neatly presented and discussed. The macroscopic fracture mode and intrinsic microscopic mechanisms governing quasi-static deformation and fracture behavior of both the CNT reinforced and unreinforced magnesium alloy is both elaborated and rationalized in light of the specific role played by presence of reinforcing phase in the magnesium alloy metal matrix, intrinsic microstructural effects and nature of loading.

Abstract: Nanocrystalline Bismuth ferrite (BiFeO₃) thin films of different thickness were deposited on glass substrates using sol-gel processing technique. The effect of thickness on structural and optical properties of BiFeO₃ thin films has been studied. The as-fired films were found to be amorphous that crystallized to hexagonal structure after annealing at 500°C for 2hr in air. The XRD pattern shows that the samples are polycrystalline in structure. At low annealing temperature (400°C), the thick film samples show amorphous in nature while thinner film shows some crystallinity with the presences of impurity phases. At high annealing temperature, all the samples show single phase distorted perovskite BiFeO₃ structure. The AFM photograph reveals that there is an increase in the grain size with the increase in film thickness. Optical transmittance spectra shows that, with the increase in film thickness, there is a decrease in transmittance (T%). Further, it is observed that increase in film thickness would lead to the decrease in optical energy band gap of the samples. The effect of thickness on the photoluminescent properties of BiFeO₃ films have also been studied for their possible application in nanoscale optoelectronic devices.

Abstract: Nafion-clay nanocomposite membrane has been prepared by dispersing unmodified and acid activated Laponite XLS in Nafion 20% dispersion. The resulting membranes possess better proton conductivity and mechanical strength as compared to the virgin membrane. Acid activation of the nanoclay leads to the in-situ generation of H₃PO₄ by the hydrolysis of the peptizer present on the surface of the nanoclay. The in-situ generated H₃PO₄ helps in improving all the technical properties of the nanocomposite including the water uptake and proton conductivity of the nanocomposite, containing acid activated clay compared to the nanocomposite, containing unmodified clay. The maximum proton conductivity of 270.2 mS/cm is achieved at 110 °C for the nanocomposite membrane containing 3% acid-activated Laponite compared to 136.2 mS/cm for the virgin Nafion. Keywords: Nafion, clay, nanocomposite, peptizer, polymer electrolyte membrane fuel cell (FEMFC), proton conductivity, membrane

Abstract: The nanocomposites containing linear low density polyethylene (LLDPE) and dodecyl amine (DA) modified graphene (DA-G) as nanofiller have been prepared by solution-mixing method and characterized. Transmission electron microscopy analysis of the nanocomposites exhibits homogeneous dispersion of graphene in the LLDPE matrix. Thermal stability of the nanocomposites with 1 wt.% DA-G are superior as compared to neat LLDPE. Gas barrier properties of the nanocomposites are also much better than that of the neat LLPDE. Co-efficient of thermal expansion values of the nanocomposites decreases with the addition of functionalized graphene. Keywords: Functionalized graphene; UV-Vis spectra; Nanocomposites; Gas barrier property; Mechanical property

Abstract: In this study, X-ray photoelectron spectroscopy (XPS) was conducted to analyze the chemical composition between epoxy matrix and nanocomposite. This experiment revealed that a chemical bonding at an interface between the matrix and nanoclay of the composites did exist. Thus, such bonding can enhance the mechanical and thermal properties of resultant polymer composites as reported in many literatures.