Recent developments in nanotechnology have demonstrated that nano-bioceramics play an important role in the biomedical field due to their superior biological and mechanical properties compared to that of conventional bioceramics. However, a long sintering duration and high temperature used in conventional sintering have remained as a challenge to preserve the nano-structure of the sintered materials. Microwave synthesis, drying and sintering of phosphate-based bioceramics have emerged in recent years as new methods which offer significant benefits against conventional methods. As a prelude, a brief discussion on the fundamental aspects of microwave and microwave heating is also introduced. Subsequently, the applications of microwave in phosphate-based bioceramics are evaluated in detail.

A study on the crystallization behavior of a soda-lime-silica glass composition incorporating rice straw ash was carried out. Melting was carried out at 1500°C in an alumina crucible for 5 hours. The glass produced was examined by differential scanning calorimetry to determine the glass transition and crystallization temperatures for use as heat-treatment temperatures to transform the glass into glass-ceramics. A similar composition made up using industrial chemicals was also melted for comparative purposes. Both glasses were heat-treated at 750°C and 920°C for 3 different soaking durations. Both glasses exhibited crystallization from the outer surface which increased in thickness as the soaking time was increased. Scanning electron microscopy was used to study the thickness and identity of the crystalline phases formed. Density and hardness measurements showed that the rice straw glass ceramics exhibited higher values than the glass-ceramics using industrial chemicals. The morphologies of the fracture surfaces of both glass-ceramic compositions were also evaluated by scanning electron microscopy.

Porous Tricalcium Phosphate (TCP) is recognized as a good biomaterial having excellent biocompatibility, biodegrability and bioresorbability. Some of the techniques to produce porous β-TCP, are replica technique (polymeric sponge method), sacrificial template method and direct forming method, however, these methods are complicated and can be costly. In this study, solid state sintering was adopted to form porous TCP as a new approach to overcome these problems. TCP bioceramic was prepared by mixing calcium hydrogen phosphate dihydrate and calcium carbonate. The powders were pressed into pellet form with four different pressures; 10, 20, 30 and 40 MPa. Then, the pellets were sintered at 1100°C to 1400°C and subsequently characterized by X-ray diffraction (XRD), density and porosity measurement, diametral tensile strength test (DTS) and scanning electron microscopy (SEM) evaluation. β-TCP phase was maintained at 1100°C and 1200°C whilst α-TCP phase had formed as second phase above 1300°C. The highest apparent porosity (60.93%) was obtained at 10 MPa and 1100°C sintering temperature, with the density of 1.12 g/cm3. The DTS values were in the range of 0.31 to 3.78 MPa in with lower DTS values were obtained at low compaction pressure and sintering temperature. Interconnected pores with high level porosity were observed at the fracture surfaces of the sintered pellets. Intraporosity was also observed. In conclusion, TCP bioceramics with interconnected pores were produced via solid state reaction; however, more work is required to improve the level of porosity.

Accurate local site response analysis allows for assessing the response of sites nearby an active seismic zone, and consequently modeling the expected earthquake behavior at the surface level. However, the modeling of this non-linear behavior is always accompanied with high uncertainty and variability that could lead to either an unsafe or a very conservative design. One way to overcome these challenges is by relying on site specific instrumentation techniques. In this study a sequential data assimilation technique is employed for real time calibration of the adopted soil model by relying on a measurement data array from different soil layers in the site of interest. The dynamic model parameters are updated in an optimal probabilistic framework using Ensemble Kalman Filter and therefore minimizing the mismatch between the measured and the predicted response of the site of interest. Due to complexities associated with inverting and updating a non-linear soil model, limited number of studies used monitoring techniques to calibrate a non-linear hysteretic soil model while incorporating different sources of uncertainties. Therefore, in this study monitored data are coupled with a non-linear dynamical model in a probabilistic setting to accurately simulate the vertical wave propagation through the soil layers of a given site. This study uses simulated vertical arrays measurements to assess the validity of the framework and to determine several practical concerns such as convergence and robustness of the presented non-linear scheme.