Zinc-substituted hydroxyapatite (Zn-HA) powders were prepared by hydrothermal method using Ca(NO(3))(2), (NH(4))(3)PO(4) and Zn(NO(3))(2 )as reagents. X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM) were used to characterize the crystalline phase, microstructure, chemical composition, morphology and thermal stability of Zn-HA. The results show that the substitution content of zinc (Zn) in Zn-HA powders prepared in NaOH solution is higher than that prepared in NH(3) solution, and is lower than that of the corresponding amount of starting materials. The substitution of the Zn ion for calcium ion causes a lower crystallinity of Zn-HA and changes the lattice parameters of Zn-HA, since the ionic radius is smaller in Zn(2+) (0.074 nm) than in Ca(2+ )(0.099 nm). Furthermore, the substitution of the Zn ions restrains the growth of Zn-HA crystal and decreases the thermal stability of Zn-HA. Zn-HA powder prepared in NH(3) solution starts to decompose at 800 degrees C when the Zn fraction increases to 15 mol%, while that prepared in NaOH solution start to decompose at 5 mol% Zn. The substitution content of Zn significantly influences the thermal stability, microstructure and morphology of Zn-HA.

No abstract

A neutrally buoyant circular particle migration in two-dimensional (2D) Poiseuille channel flow driven by pulsatile velocity is numerical studied by using immersed boundary-lattice Boltzmann method (IB-LBM). The effects of Reynolds number (25≤Re≤200) and blockage ratio (0.15≤k≤0.40) on particle migration driven by pulsatile and non-pulsatile velocity are all numerically investigated for comparison. The results show that, different from non-pulsatile cases, the particle will migrate back to channel centerline with underdamped oscillation during the time period with zero-velocity in pulsatile cases. The maximum lateral travel distance of the particle in one cycle of periodic motion will increase with increasing Re, while k has little impact. The quasi frequency of such oscillation has almost no business with Re and k. Moreover, Re plays an essential role in the damping ratio. Pulsatile flow field is ubiquitous in aorta and other arteries. This article is conducive to understanding nanoparticle migration in those arteries.

No abstract

The inertial migration of two-dimensional soft particles initially distributed uniformly in channel flow is numerically studied by employing an immersed-boundary lattice Boltzmann method coupled with a finite element method. To model a soft particle, a capsule with an elastic membrane separating the liquid inside from the outside is used. Validation tests show excellent agreement with previous numerical results of other researchers. Then the effects of the number of capsules $N_p$, the bending stiffness $E_b$, the initial position $Y_0^\prime$, and the Reynolds number $Re$ on the dynamics of the capsules in channel flow are investigated in detail. Interestingly, we discover a new regime (labeled as regime E) in which a few capsules situated near the channel centerline travel much faster than the rest. Moreover, regime E is more prone to vanishing while the capsules are very soft. The normalized overall lateral position of the capsules $\sigma$ increases almost linearly with $N_p$ when the capsules stabilize in a single-line particle train (designated as regime A). We also make an effort to explain the formation of the capsule deformation shape in regime A. The steady dynamics of a single capsule depend on whether the initial position is on the channel centerline. However, if the capsule is not released on the channel centerline, the steady capsule dynamics are independent of the initial position. But it is not true for multiple capsule dynamics. These findings may help to understand the inertial migration of capsules in channel flow.