AbstractsBiology & Animal Science

This thesis combines four manuscripts of which I am the first author. The first manuscript examines the phase separation process and related process parameters. This article provides detailed experimental results of the delivery and separation process. During the delivery of 40% Liquid-to-Powder-Ratio (LPR) paste, only 62[plus ou moins]3 % of the paste initially present in the 10-mL syringe could be injected. Thereafter, the remaining paste in the syringe was not amendable to injection suggesting the existence of liquid separation. The LPR of the extruded fraction of a 37% LPR paste ranged from 40.9[plus ou moins]2.0 % to 42.7[plus ou moins]2.1 %. On the other hand, a shortage of water content was measured for the paste left in the syringe. Furthermore, this shortage was gradual, ranging from 27.3[plus ou moins]1.9 % at the plunger side to 30.9[plus ou moins]1.6 % at the tip side. In addition, this article presents rheological measurements of the paste showing clearly that the limitation was not related to the viscosity of the paste but rather to the phase separation process. Specifically, the yield stresses were around 66[plus ou moins]2 Pa, 19[plus ou moins]2 Pa, and 8[plus ou moins]0 Pa for 40%, 50%, and 65% LPR suspensions, respectively. For the three studied LPRs, the viscosity rapidly dropped with an increase of shear rate to a level below 10 Pas. The second manuscript examines the possibility that fine particles migrate faster than large particles during injection, hence leading to a so-called size separation. This size separation process can be expected from the scientific literature, but had not been investigated prior to my study. In a way, the size separation is very similar to the phase separation process. An electrohydraulic system was used to control the delivery process. The result of this second study, showed no evidence of size separation. It was therefore concluded that the main mechanism underlying the limited injectability is the liquid phase filtration through the porous particles bed of the paste. The third manuscript examines the role of powder porosity ([epsilon]) and permeability. For that purpose, an electronically assisted device was used to measure the powder permeability. In this study, three powders were examined for comparison and better understanding. In addition, the powder permeability was correlated with the paste injectability. Adding 3 wt% of a fine nanosized powder to the [bêta]-TCP powder decreased the mixture permeability at a porosity of [varepsilon] = 67.5% from 6.4.10[exposant]-13 m[exposant]2 to 5.6.10[exposant]-13 m[exposant]2 and increased the injected volume fraction from 70.8[plus ou moins]1.9 % to 84.5[plus ou moins]0.9 %. The results showed clear evidence that the injectability can be improved by admixing different powders. However, permeability was not a strong predictor of the liquid separation phenomenon. The last manuscript provides a practical solution to reduce phase separation occurrence. For that purpose an ultrasonication process was suggested and applied…