The sintering behaviour of synthesized HA powder that was calcined at various temperatures ranging from 700 degrees C to 1000 degrees C was investigated in terms of phase stability, bulk density, Young's modulus and Vickers hardness. The calcination treatment resulted in higher crystallinity of the starting HA powder. Decomposition of HA phase to form secondary phases was not observed in all the calcined powders. The results also indicated that powder calcination (up to 900 degrees C) prior to sintering has negligible effect on the sinterability of the HA compacts. However, powder calcined at 1000 degrees C was found to be detrimental to the properties of sintered hydroxyapatite bioceramics.
The sintering behaviour of a commercial HA and synthesized HA was investigated over the temperature range of 700 degrees C to 1400 degrees C in terms of phase stability, bulk density, Young's modulus and Vickers hardness. In the present research, a wet chemical precipitation reaction was successfully employed to synthesize a submicron, highly crystalline, high purity and single phase stoichiometric HA powder that is highly sinteractive particularly at low temperature regimes below 1100 degrees C. It has been revealed that the sinterability of the synthesized HA was significantly greater than that of the commercial HA. The temperature for the onset of sintering and the temperature required to achieve densities above 98% of theoretical value were approximately 150 degrees C lower for the synthesized HA than the equivalent commercial HA. Nevertheless, decomposition of HA phase upon sintering was not observed in the present work for both powders.
Triboelectric nanogenerators (TENGs) have been extensively investigated as both energy harvesters and self-powered sensors. While their application as force sensors has been widely reported, the use of TENGs as stretch sensors remains relatively unexplored. Stretch sensors are important for monitoring human joint and limb movements, with significant potential in rehabilitation applications such as post-stroke therapy and recovery following knee surgery. In this work, we present a preliminary TENG-based stretch sensor comprising a multi-triangular elastomer structure and an arched copper electrode. The primary objective is to establish the viability of the sensing concept and validate its fundamental operating principle. The device generates an output voltage that is proportional to the bending angle. This behavior arises from the increased contact and friction between the elastomer (Dragon Skin silicone) and copper layers as deformation increases, resulting in enhanced triboelectric charge generation and a higher output voltage. Owing to the inherent capacitive characteristics of the TENG under high-impedance loading conditions, the generated voltage can be retained for several seconds after the bending motion ceases. This retention time is sufficient for signal acquisition and joint-motion detection electronics. Experimental results demonstrate that the proposed TENG-based stretch sensor can reliably measure bending angles under both quasi-static and dynamic operating conditions, highlighting its potential for wearable motion-monitoring and rehabilitation systems.