Vol 1, No 1 (2020)

Electrophoretic deposition (EPD) technique is used to prepare zirconia–alumina composite layers based on the principle of functionally graded materials (FGM). The FGM were prepared with five layers. The outer layer was composed of pure α-alumina to promote biocompatibility while the inner layer was stabilised zirconia (3Y-TZP), to benefit from its tough properties. The intermediate layers were stepwise graded layers. The stability of the EPD suspensions was the main challenge during the preparation steps. Due to availability and low cost, alcoholic solutions of polyethylene glycol (PEG) and toluene were used to control conductivity, dielectric constant and the viscosity of the suspension. The appropriately applied potential, (ζ), for the deposition of each layer, was achieved via gradation of the applied voltage, which was to optimise the packing of each layer and avoid cracking after sintering at 1500 °C. The cylindrical-shaped green specimens were obtained via deposition on graphite electrodes. A small amount of acetic acid was added during the deposition of the final outer alumina layer to introduce porosity, via the bubbling of acetic acid, to encourage osseointegration. The sintered specimens were implanted in rabbit tibial bone. In vivo histological tests showed the successful osseointegration of the implants to the rabbit bone.

In this work, an attempt has been made to improve the sand casting process by reducing the percentage of casting defects. The enhancement of the sand casting process is based on producing green sand castings with good pattern profiles and no failures at any complex ‎points during the separation process, handling and transportation. This work ‎introduces modified, non-destructive, direct tests for measuring sand mould ‎properties using sensor readings. ‎A new flowability sensor has been used to measure the time-dependent density, ‎distance-dependent mould hardness, and distance-dependent mould strength. The ‎sensor is able to detect sand motion at the desired points during the mould-making process. The live characterisation of the green sand mould is used to determine the optimum ‎parameters for the compaction process, reduction of the moulding time, and spent ‎energy, so that the cost of the moulding and casting process will be reduced.‎ It has been found that there is a linear relationship between the properties of the green sand samples and the sensor signals. The new method facilitates the measurement of sand properties and determines the most effective moulding parameters based on the flowability sensor readings. The resultant increases in both compactibility and compaction pressure improve mould hardness and mould strength.

In this work, nanocomposite material consisting of titanium dioxide (TiO₂) nanoparticles and rhodamine 6G (R6G) laser dye was doped with different ratios of polystyrene (PS) and polymethylmethacrylate (PMMA) polymer blends (i.e. 40% PS/60% PMMA and 50% PS/50% PMMA) using the casting method. The optical properties of the prepared samples were measured using UV-visible spectroscopy. These measurements include the calculations of the absorption (A%), absorption coefficient (α), energy gap (Eg), refractive index (n), extinction coefficient (K) and real and imaginary parts. These nanocomposite materials were investigated using a scanning electron microscope and photoluminescence (PL) spectra emission. The SEM results show that the optimum results were at 50% PS/50% PMMA/TiO₂/R6G with all the dye being decorated in the process blend, while the TiO₂ nanoparticle demonstrated that the pores were incomplete in some places and complete in others. The optical results show that there are red shifts in all absorption peaks caused by the increased PS ratio. The Eg decreased from 3.2 eV to 2.8 eV as the concentration of PS in the polymer matrix increased. The PL spectrum for the nanocomposites, with a different ratio of PS, shows that sharp peaks of PL emission occur at a wavelength of 570 nm and shift towards longer wavelengths with an increased PS%.